siemens/mc_bdx1: Enable decoding for COM 3 & COM 4 on LPC

Since this mainboard provides 4 COM ports on LPC, enable decoding of
the corresponding addresses using the generic LPC decode registers.

Change-Id: I0e93d40dca01d55f3567a18c7ec02269e3bec466
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/16535
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/fsp_broadwell_de/include/soc/lpc.h

@@ -25,6 +25,10 @@
 #define PIRQ_RCR2		0x68
 #define LPC_IO_DEC		0x80
 #define LPC_EN			0x82
+#define LPC_GEN1_DEC		0x84
+#define LPC_GEN2_DEC		0x88
+#define LPC_GEN3_DEC		0x8c
+#define LPC_GEN4_DEC		0x90
 #define GEN_PMCON_1		0xA0
 #define GEN_PMCON_2		0xA2
 #define GEN_PMCON_3		0xA4