zephyr/kconfig: put KB protocol because KB option
zephyr/kconfig: put KB protocol because KB option

The PLATFORM_EC_KEYBOARD_PROTOCOL_8042 should be guarded
by the PLATFORM_EC_KEYBOARD option.

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

Signed-off-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>
Change-Id: Idd070454a11ed65cab763ff7788dec4b907f610d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2530152
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