zephyr/gpio: add bound checks to all gpio functions
zephyr/gpio: add bound checks to all gpio functions

The static check for zephyr will generate warnings if we
do not bounds check the incoming gpio_signal enum. We should
bounds check anyway.

BRANCH=none
BUG=b:172512307
TEST=build posix-ec with CL stack

Signed-off-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>
Change-Id: I1b2014c02e02d7271eeabd3cc041b3c452b1c43f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2530151
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>

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