ide/pci/sis5513.c: add missing "else"

This patch adds a missing "else" that was missing in
commit c77a89cd.

Spotted by the Coverity checker.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>,
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>