[SCSI] megaraid: add __devexit annotation

megaraid_remove_one() can become __devexit.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: "Patro, Sumant" <Sumant.Patro@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>