The GPIO console commands are common to all platform, let's push them in
the common code.
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BUG=None
TEST=make BOARD=link && make BOARD=bds && make BOARD=discovery
on BDS console, try gpioget command.
Change-Id: I26e6d26b8d661e78b80d5d5f665e81f4daef0c11