Blackfin: gpio: add a debounce stub

The GPIO API was extended recently to include debounce functions, but
since the on-chip Blackfin GPIO modules don't support this stuff, make
a stub in the non-GPIOLIB case so drivers build properly.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

diff --cc arch/blackfin/include/asm/gpio.h
Simple merge