[SCSI] bfa: remove a file with small size

Removed bfa_drv.c, merged it to bfa_core.c and modified Makefile.

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