scsi: aha1542: avoid uninitialized variable warnings

Gcc incorrectly detects that two variables in aha1542_queuecommand might
be used without an initialization:

scsi/aha1542.c: In function 'aha1542_queuecommand':
scsi/aha1542.c:382:16: error: 'cptr' may be used uninitialized in this function [-Werror=maybe-uninitialized]
scsi/aha1542.c:379:11: error: 'sg_count' may be used uninitialized in this function [-Werror=maybe-uninitialized]

The only user of these is doing the same check that the assigment has,
so it is actually guaranteed to work. Adding an "else" clause with a
fake initialization shuts up the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>