mb/google/skyrim: Disable unused SPI ROM types

By default, coreboot includes support for all the different types of SPI
ROMs.  Excluding the unused ROM types shrinks ramstage by almost 4k.

BUG=b:267735039
TEST=Build & Boot ROM
BRANCH=Skyrim

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: If6e402269d1f2cac8256d478eb36743441497bdf
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72769
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jon Murphy <jpmurphy@google.com>

src/mainboard/google/skyrim/Kconfig

@@ -199,4 +199,21 @@ config ENABLE_STB_SPILL_TO_DRAM
 config CARDBUS_PLUGIN_SUPPORT
 	default n
 
+# Exclude support for SPI ROM types that won't be used on Skyrim platforms
+config SPI_FLASH_DONT_INCLUDE_ALL_DRIVERS
+	default y
+
+# Gigadevice is used on Whiterun as an alternative to Winbond
+config SPI_FLASH_GIGADEVICE
+	default y
+
+# XMC chips used on Markarth as an alternative to Winbond
+# These chips identify as ST Micro (Manufacturer ID: 0x20)
+config SPI_FLASH_STMICRO
+	default y
+
+# Winbond chips are used by all Skyrim devices as the primary flash chip
+config SPI_FLASH_WINBOND
+	default y
+
 endif # BOARD_GOOGLE_BASEBOARD_SKYRIM