vfio/pci: Resolve sparse endian warnings in IGD support

Sparse warns:

sparse warnings: (new ones prefixed by >>)
>> drivers/vfio/pci/vfio_pci_igd.c:146:21: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned short [addressable] [usertype] val @@     got restricted __le16 [usertype] @@
   drivers/vfio/pci/vfio_pci_igd.c:146:21: sparse:     expected unsigned short [addressable] [usertype] val
   drivers/vfio/pci/vfio_pci_igd.c:146:21: sparse:     got restricted __le16 [usertype]
>> drivers/vfio/pci/vfio_pci_igd.c:161:21: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int [addressable] [usertype] val @@     got restricted __le32 [usertype] @@
   drivers/vfio/pci/vfio_pci_igd.c:161:21: sparse:     expected unsigned int [addressable] [usertype] val
   drivers/vfio/pci/vfio_pci_igd.c:161:21: sparse:     got restricted __le32 [usertype]
   drivers/vfio/pci/vfio_pci_igd.c:176:21: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned short [addressable] [usertype] val @@     got restricted __le16 [usertype] @@
   drivers/vfio/pci/vfio_pci_igd.c:176:21: sparse:     expected unsigned short [addressable] [usertype] val
   drivers/vfio/pci/vfio_pci_igd.c:176:21: sparse:     got restricted __le16 [usertype]

These are due to trying to use an unsigned to store the result of
a cpu_to_leXX() conversion.  These are small variables, so pointer
tricks are wasteful and casting just generates different sparse
warnings.  Store to and copy results from a separate little endian
variable.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/202111290026.O3vehj03-lkp@intel.com/
Link: https://lore.kernel.org/r/163840226123.138003.7668320168896210328.stgit@omen
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Author: Alex Williamson

drivers/vfio/pci/vfio_pci_igd.c

@@ -309,13 +309,14 @@ static ssize_t vfio_pci_igd_cfg_rw(struct vfio_pci_core_device *vdev,
 
 	if ((pos & 3) && size > 2) {
 		u16 val;
+		__le16 lval;
 
 		ret = pci_user_read_config_word(pdev, pos, &val);
 		if (ret)
 			return ret;
 
-		val = cpu_to_le16(val);
-		if (copy_to_user(buf + count - size, &val, 2))
+		lval = cpu_to_le16(val);
+		if (copy_to_user(buf + count - size, &lval, 2))
 			return -EFAULT;
 
 		pos += 2;
@@ -324,13 +325,14 @@ static ssize_t vfio_pci_igd_cfg_rw(struct vfio_pci_core_device *vdev,
 
 	while (size > 3) {
 		u32 val;
+		__le32 lval;
 
 		ret = pci_user_read_config_dword(pdev, pos, &val);
 		if (ret)
 			return ret;
 
-		val = cpu_to_le32(val);
-		if (copy_to_user(buf + count - size, &val, 4))
+		lval = cpu_to_le32(val);
+		if (copy_to_user(buf + count - size, &lval, 4))
 			return -EFAULT;
 
 		pos += 4;
@@ -339,13 +341,14 @@ static ssize_t vfio_pci_igd_cfg_rw(struct vfio_pci_core_device *vdev,
 
 	while (size >= 2) {
 		u16 val;
+		__le16 lval;
 
 		ret = pci_user_read_config_word(pdev, pos, &val);
 		if (ret)
 			return ret;
 
-		val = cpu_to_le16(val);
-		if (copy_to_user(buf + count - size, &val, 2))
+		lval = cpu_to_le16(val);
+		if (copy_to_user(buf + count - size, &lval, 2))
 			return -EFAULT;
 
 		pos += 2;