Tegra: kbc: Allow keypresses during startup Add support to detect keys pressed before keyboard driver is loaded. BUG=chromium-os:17229 TEST=Built and tested on Seaboard. Reset seaboard keeping any key pressed and verify system enters u-boot console. Change-Id: I7508c901b79bf92be755a6e81a9556ccba4c78b1 Signed-off-by: Rakesh Iyer <riyer@nvidia.com> Reviewed-on: http://gerrit.chromium.org/gerrit/4964 Reviewed-by: Simon Glass <sjg@chromium.org>