ARM: rmobile: Add missing rcar-common/common.c to Beacon RZG2M kit

The rcar-common/common.c contains various common board functions shared
by all R-Car and RZG boards. This board is not compiling the file in, so
add it. This way, part of the board code can be de-duplicated too.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Adam Ford <aford173@gmail.com>

board/beacon/beacon-rzg2m/Makefile

@@ -6,4 +6,4 @@
 # SPDX-License-Identifier: GPL-2.0+
 #
 
-obj-y	:= beacon-rzg2m.o
+obj-y	:= beacon-rzg2m.o ../../renesas/rcar-common/common.o

board/beacon/beacon-rzg2m/beacon-rzg2m.c

@@ -28,21 +28,6 @@ int board_init(void)
 	return 0;
 }
 
-int dram_init(void)
-{
-	if (fdtdec_setup_mem_size_base() != 0)
-		return -EINVAL;
-
-	return 0;
-}
-
-int dram_init_banksize(void)
-{
-	fdtdec_setup_memory_banksize();
-
-	return 0;
-}
-
 #define RST_BASE	0xE6160000
 #define RST_CA57RESCNT	(RST_BASE + 0x40)
 #define RST_CODE	0xA5A5000F