soc/intel/quark: Add legacy SPI flash controller driver

Add SPI driver code for the legacy SPI flash controller.  Enable erase
and write support allowing coreboot to save non-volatile data into
the SPI flash.

TEST=Build and run on Galileo Gen2.

Change-Id: I8f38c955d7c42a1e58728c728d0cecc36556de5c
Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Reviewed-on: https://review.coreboot.org/20231
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/quark/Kconfig

@@ -36,6 +36,7 @@ config CPU_SPECIFIC_OPTIONS
 	select SOC_INTEL_COMMON
 	select SOC_INTEL_COMMON_RESET
 	select SOC_SETS_MSRS
+	select SPI_FLASH
 	select TSC_CONSTANT_RATE
 	select UART_OVERRIDE_REFCLK
 	select UDELAY_TSC