drives/spi/spi_flash: add option to not select all drivers

Add a new Kconfig option, SPI_FLASH_DONT_INCLUDE_ALL_DRIVERS,
to make it easier for other parts of the code base to indicate that
all spi flash drivers should not be included.

Change-Id: Ibf2c4f1d2b8a73cff14bb627ddf759d7970920ea
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38362
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/skylake/Kconfig

@@ -77,6 +77,7 @@ config CPU_SPECIFIC_OPTIONS
 	select TSC_SYNC_MFENCE
 	select UDELAY_TSC
 	select UDK_2015_BINDING
+	select SPI_FLASH_DONT_INCLUDE_ALL_DRIVERS
 
 config FSP_HYPERTHREADING
 	bool "Enable Hyper-Threading"
@@ -232,10 +233,6 @@ config FSP_FD_PATH
 	depends on FSP_USE_REPO
 	default "3rdparty/fsp/KabylakeFspBinPkg/Fsp.fd"
 
-config SPI_FLASH_INCLUDE_ALL_DRIVERS
-	bool
-	default n
-
 config MAX_ROOT_PORTS
 	int
 	default 24