mb/google/*: Use newly added Chrome EC boardid function

Instead of duplicating code across multiple mainboards, use newly
added helper function to read boardid from Chrome EC.

Change-Id: I1671c0a0b87d0c4c45da5340e8f17a4a798317ca
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/21682
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/mainboard/intel/strago/Kconfig

@@ -4,6 +4,7 @@ config BOARD_SPECIFIC_OPTIONS
 	def_bool y
 	select BOARD_ROMSIZE_KB_8192
 	select EC_GOOGLE_CHROMEEC
+	select EC_GOOGLE_CHROMEEC_BOARDID
 	select EC_GOOGLE_CHROMEEC_MEC
 	select EC_GOOGLE_CHROMEEC_ACPI_MEMMAP
 	select ENABLE_BUILTIN_COM1