convert bnx2i_dev_lock to type mutex from rwlock_t because
cnic->register_device() can sleep for various reasons including memory
allocation, waiting for ISCSI_INIT completion and while acquiring mutex lock,
cnic_lock.
Signed-off-by: Michael Chan <mchan@broadcom.com> Signed-off-by: Anil Veerabhadrappa <anilgv@broadcom.com> Reviewed-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Signed-off-by: James Bottomley <James.Bottomley@suse.de>