RDMA/uverbs: Add empty rdma_uattrs_has_raw_cap() declaration

The call to rdma_uattrs_has_raw_cap() is placed in mlx5 fs.c file,
which is compiled without relation to CONFIG_INFINIBAND_USER_ACCESS.

Despite the check is used only in flows with CONFIG_INFINIBAND_USER_ACCESS=y|m,
the compilers generate the following error for CONFIG_INFINIBAND_USER_ACCESS=n
builds.

>> ERROR: modpost: "rdma_uattrs_has_raw_cap" [drivers/infiniband/hw/mlx5/mlx5_ib.ko] undefined!

Fixes: f458ccd ("RDMA/uverbs: Check CAP_NET_RAW in user namespace for flow create")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202507080725.bh7xrhpg-lkp@intel.com/
Link: https://patch.msgid.link/72dee6b379bd709255a5d8e8010b576d50e47170.1751967071.git.leon@kernel.org
Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>

Author: rleon

include/rdma/ib_verbs.h

@@ -4810,15 +4810,19 @@ struct ib_ucontext *ib_uverbs_get_ucontext_file(struct ib_uverbs_file *ufile);
 
 #if IS_ENABLED(CONFIG_INFINIBAND_USER_ACCESS)
 int uverbs_destroy_def_handler(struct uverbs_attr_bundle *attrs);
+bool rdma_uattrs_has_raw_cap(const struct uverbs_attr_bundle *attrs);
 #else
 static inline int uverbs_destroy_def_handler(struct uverbs_attr_bundle *attrs)
 {
 	return 0;
 }
+static inline bool
+rdma_uattrs_has_raw_cap(const struct uverbs_attr_bundle *attrs)
+{
+	return false;
+}
 #endif
 
-bool rdma_uattrs_has_raw_cap(const struct uverbs_attr_bundle *attrs);
-
 struct net_device *rdma_alloc_netdev(struct ib_device *device, u32 port_num,
 				     enum rdma_netdev_t type, const char *name,
 				     unsigned char name_assign_type,