soc/intel/common: Enable decoding of the COMB range to LPC based on Kconfig

soc/intel/common: Enable decoding of the COMB range to LPC based on Kconfig

By default all Intel platform has enable IO decode range for COMA if
CONFIG_DRIVERS_UART_8250IO is selected.

With this patch, COMB will get enable based on
CONFIG_SOC_INTEL_COMMON_BLOCK_LPC_COMB_ENABLE Kconfig selection.

Also make lpc_enable_fixed_io_ranges() function returns Enabled I/O bits to avoid
an additional pci configuration read to get the same data.

Change-Id: I884dbcc8a37cf8551001d0ca61910c986b903ebc
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/25045
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Rizwan Qureshi <rizwan.qureshi@intel.com>