Reverse HAS_BUTTON logic since most webcams either have a button or if
they don't don't bother to send any interrupts. However I have at least
one model that appears to leave the button GPIO floating and can send
a bogus interrupt.
Signed-off-by: Brian Johnson <brijohn@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>