[SCSI] bfa: rename log_level to bfa_log_level

Rename log_level to bfa_log_level to make the global variable more bfa
specific and avoid clashes with other drivers which was causing a
build failure.

Signed-off-by: Jing Huang <huangj@brocade.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>