RDMA/bnxt_re: Add sanity checks on rdev validity

RDMA/bnxt_re: Add sanity checks on rdev validity

There is a possibility that ulp_irq_stop and ulp_irq_start
callbacks will be called when the device is in detached state.
This can cause a crash due to NULL pointer dereference as
the rdev is already freed.

Fixes: cc5b9b48d447 ("RDMA/bnxt_re: Recover the device when FW error is detected")
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Link: https://patch.msgid.link/1738657285-23968-3-git-send-email-selvin.xavier@broadcom.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>