mkbp: Limit the visibility of MKBP FIFO variables

There is no need to keep the mkbp FIFO variables visible outside the
driver. Declare them as static instead.

BUG=None
BRANCH=None
TEST=Compiles successfully. Button presses still work on poppy.

Change-Id: If0fd6101568ce2e54e26f171a695a894c961f37f
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/516244
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
1 file changed