mb/system76/*: CMOS: Drop power_on_after_fail option

Our boards do not boot if power_on_after_fail=Disable. Drop the option
and use the default of powering on.

Change-Id: Ia1857e52f838337048f79f8ca5c12d669cae321a
Signed-off-by: Tim Crawford <tcrawford@system76.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58673
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jeremy Soller <jeremy@system76.com>

src/mainboard/system76/galp5/cmos.default

@@ -1,3 +1,2 @@
 boot_option=Fallback
 debug_level=Debug
-power_on_after_fail=Enable