soc/intel/skylake: Clean up code by using common FAST_SPI module

This patch currently contains the following -
 1. Use SOC_INTEL_COMMON_BLOCK_FAST_SPI kconfig for common FAST_SPI code.
 2. Perform FAST_SPI programming by calling APIs from common FAST_SPI library.
 3. Use common FAST_SPI header file.

Change-Id: I4fc90504d322db70ed4ea644b1593cc0605b5fe8
Signed-off-by: Barnali Sarkar <barnali.sarkar@intel.com>
Reviewed-on: https://review.coreboot.org/19055
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/src/soc/intel/skylake/Kconfig b/src/soc/intel/skylake/Kconfig
index 95cf330..515de91 100644
--- a/src/soc/intel/skylake/Kconfig
+++ b/src/soc/intel/skylake/Kconfig
@@ -50,6 +50,7 @@
 	select SOC_INTEL_COMMON
 	select SOC_INTEL_COMMON_ACPI_WAKE_SOURCE
 	select SOC_INTEL_COMMON_BLOCK
+	select SOC_INTEL_COMMON_BLOCK_FAST_SPI
 	select SOC_INTEL_COMMON_BLOCK_GSPI
 	select SOC_INTEL_COMMON_BLOCK_ITSS
 	select SOC_INTEL_COMMON_BLOCK_LPSS