soc/intel/common/block: Move common uart function to block/uart

This patch moves uart functions which are common across multiple soc to
block/uart. This will remove redundant code copy from soc
{skylake/apollolake/cannonlake}.

BUG=b:78109109
BRANCH=none
TEST=Build and boot on KBL/APL/CNL platform.

Change-Id: I109d0e5c942e499cb763bde47cb7d53dfbf5cef6
Signed-off-by: Maulik V Vaghela <maulik.v.vaghela@intel.com>
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/26164
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/skylake/Kconfig

@@ -64,6 +64,7 @@ config CPU_SPECIFIC_OPTIONS
 	select SOC_INTEL_COMMON_BLOCK_SGX
 	select SOC_INTEL_COMMON_BLOCK_SMM
 	select SOC_INTEL_COMMON_BLOCK_SMM_IO_TRAP
+	select SOC_INTEL_COMMON_BLOCK_UART
 	select SOC_INTEL_COMMON_BLOCK_VMX
 	select SOC_INTEL_COMMON_PCH_BASE
 	select SOC_INTEL_COMMON_NHLT