[SCSI] aic94xx: Match request_firmware with release_firmware

The vmalloc() blob holding the sequencer firmware wasn't being released at
module unload time, which resulted in a memory leak.

Signed-off-by: Alexis Bruemmer <alexisb@us.ibm.com>
Acked-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>