IB/rxe: Fix a MR reference leak in check_rkey()

IB/rxe: Fix a MR reference leak in check_rkey()

[ Upstream commit b3a459961014b14c267544c327db033669493295 ]

Avoid that calling check_rkey() for mem->state == RXE_MEM_STATE_FREE
triggers an MR reference leak.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Andrew Boyer <andrew.boyer@dell.com>
Cc: Moni Shoua <monis@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>