RDMA/bnxt_re: Remove unused vlan_tag variable

The Broadcom driver produces the following compilation warning

drivers/infiniband/hw/bnxt_re/ib_verbs.c:
	In function ‘bnxt_re_create_ah’:
drivers/infiniband/hw/bnxt_re/ib_verbs.c:668:6:
	warning: variable ‘vlan_tag’ set but not used [-Wunused-but-set-variable]
	u16 vlan_tag;

Let's remove it till vlan_tag will be implemented properly.

Cc: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>