kblight: fix bounds checks on backlight intensity
kblight: fix bounds checks on backlight intensity

looks like we were performing the bounds check on a global variable
instead of the input to the function...

BUG=none
BRANCH=none
TEST=EC console kblight command now correctly catches out of range
	values

Change-Id: Ia54e42bfbc284eea64f7e6f7defaa2400c20e471
Signed-off-by: Caveh Jalali <08e24a66aefda7a55ca7d73f8903e0fb16eec763@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1175544
Commit-Ready: caveh jalali <08e24a66aefda7a55ca7d73f8903e0fb16eec763@chromium.org>
Tested-by: caveh jalali <08e24a66aefda7a55ca7d73f8903e0fb16eec763@chromium.org>
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>
Reviewed-by: caveh jalali <08e24a66aefda7a55ca7d73f8903e0fb16eec763@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec