mailbox: pcc: Use acpi_os_ioremap() instead of ioremap()

The Platform Communication Channel (PCC) mailbox driver currently uses
ioremap() to map channel shared memory regions. However it is preferred
to use acpi_os_ioremap(), which is mapping function specific to EFI/ACPI
defined memory regions. It ensures that the correct memory attributes
are applied when mapping ACPI-provided regions.

While at it, also add checks for handling any errors with the mapping.

Acked-by: Huisong Li <lihuisong@huawei.com>
Tested-by: Huisong Li <lihuisong@huawei.com>
Tested-by: Adam Young <admiyo@os.amperecomputing.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: sudeep-holla

drivers/mailbox/pcc.c

@@ -419,8 +419,12 @@ int pcc_mbox_ioremap(struct mbox_chan *chan)
 		return -1;
 	pchan_info = chan->con_priv;
 	pcc_mbox_chan = &pchan_info->chan;
-	pcc_mbox_chan->shmem = ioremap(pcc_mbox_chan->shmem_base_addr,
-				       pcc_mbox_chan->shmem_size);
+
+	pcc_mbox_chan->shmem = acpi_os_ioremap(pcc_mbox_chan->shmem_base_addr,
+					       pcc_mbox_chan->shmem_size);
+	if (!pcc_mbox_chan->shmem)
+		return -ENXIO;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pcc_mbox_ioremap);