drivers/spi/tpm: provide Kconfig to indicate CR50 usage

Going forward it's important to note when a CR50 is expected
to be present in the system. Additionally, this Kconfig addition
provides symmetry with the equivalent i2c Kconfig option.

BUG=b:35775104

Change-Id: Ifbd42b8a22f407534b23459713558c77cde6935d
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/18680
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)

src/drivers/spi/tpm/Kconfig

@@ -11,3 +11,8 @@ config DRIVER_TPM_SPI_CHIP
 	int "Chip Select of the TPM chip on its SPI bus"
 	default 0
 	depends on SPI_TPM
+
+config MAINBOARD_HAS_SPI_TPM_CR50
+	bool
+	default n
+	depends on SPI_TPM

src/mainboard/google/gru/Kconfig

@@ -48,6 +48,7 @@ config BOARD_SPECIFIC_OPTIONS
 config CHROMEOS
 	select EC_GOOGLE_CHROMEEC_SWITCHES
 	select EC_SOFTWARE_SYNC
+	select MAINBOARD_HAS_SPI_TPM_CR50 if GRU_HAS_TPM2
 	select SPI_TPM if GRU_HAS_TPM2
 	select VBOOT_VBNV_FLASH
 	select VIRTUAL_DEV_SWITCH