serial_8250: pci_enable_device fail is not fully handled

<rmk> talking about leaks - I noticed that the 'check return of
pci_enable_dev()' in the 8250 pci resume function finally made it in
despite my objections against it (causing stuff in higher levels to
leak).

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>