mb/google/rauru: Initialize flash controller in bootblock

Initialize SPI NOR Flash Controller (SNFC) in the bootblock.

TEST=read nor flash data successfully.
BUG=b:317009620

Change-Id: I88960ce7a50f67ea6f402884b714cb205836a6d8
Signed-off-by: Noah Shen <noah.shen@mediatek.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83924
Reviewed-by: Yidi Lin <yidilin@google.com>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/rauru/Kconfig

@@ -27,4 +27,8 @@ config MAINBOARD_DIR
 config MAINBOARD_PART_NUMBER
 	string
 	default "Rauru" if BOARD_GOOGLE_RAURU
+
+config BOOT_DEVICE_SPI_FLASH_BUS
+	int
+	default 8
 endif

src/mainboard/google/rauru/bootblock.c

@@ -1,8 +1,9 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <bootblock_common.h>
+#include <soc/spi.h>
 
 void bootblock_mainboard_init(void)
 {
-	/* TODO: add mainboard init for bootblock */
+	mtk_snfc_init();
 }