[media] ngene: better comment unused code to avoid warnings

get rid of a few warnings about empty body:
drivers/media/pci/ngene/ngene-core.c:756:3: warning: suggest braces around empty body in an 'else' statement [-Wempty-body]
drivers/media/pci/ngene/ngene-cards.c:429:5: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
Those are due to some commented code.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>