scsi: qla2xxx: Enable type checking for the SRB free and done callback functions

Since all pointers passed to the srb_t.done() and srb_t.free() functions
have type srb_t, change the type of the first argument of these functions
from void * into struct srb *. This allows the compiler to verify the
argument types for these functions. This patch does not change any
functionality.

Cc: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>