[SCSI] aacraid: READ_CAPACITY_16 shouldn't trust allocation length in cdb

When aacraid spoofs READ_CAPACITY_16, it assumes that the data length
in the sg list is equal to allocation length in cdb. But sg can put
any value in scb so the driver needs to check both the data length in
the sg list and allocation length in cdb.

If allocation length is larger than the response length that the
driver expects, it clears the data buffer in the sg list to zero but
it doesn't need to do. Just setting resid is fine.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Mark Salyzyn <Mark_Salyzyn@adaptec.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>