mb/google/octopus/var/garg: fix LTE power sequence in reboot state

invoke LTE power off function to meet LTE power sequence while DUT is
in reboot state.

BUG=b:167565015
BRANCH=octopus
TEST=build and verify on the DUT with LTE

Change-Id: I825cefb524ddaf9a9cb6add31c2ee0eea484f978
Signed-off-by: Kevin Chiu <kevin.chiu@quantatw.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46022
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Marco Chen <marcochen@google.com>
Reviewed-by: Henry Sun <henrysun@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/octopus/variants/garg/Makefile.inc

@@ -2,3 +2,5 @@ bootblock-y += gpio.c
 
 ramstage-y += gpio.c
 ramstage-y += variant.c
+
+smm-y += variant.c