scsi: aic7xxx: remove aiclib.c

aiclib.c is unused (and contains no code) since commit 1ff92730
("[SCSI] aic7xxx: remove aiclib.c")

13 years later, finish the cleaning by removing it from tree.

[mkp: tweaked patch description]

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>