drivers: renesas: watchdog: Move to common

Move watch driver code to common directory, so that the same
code can be re-used by both R-Car Gen3 and RZ/G2 platforms.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Change-Id: I235f2cde325a0feeadbfc4b7ee02e8b1186f7ea1
diff --git a/plat/renesas/common/common.mk b/plat/renesas/common/common.mk
index 09ff1d5..adee49b 100644
--- a/plat/renesas/common/common.mk
+++ b/plat/renesas/common/common.mk
@@ -91,6 +91,7 @@
 			drivers/renesas/common/emmc/emmc_init.c		\
 			drivers/renesas/common/emmc/emmc_read.c		\
 			drivers/renesas/common/emmc/emmc_cmd.c		\
+			drivers/renesas/common/watchdog/swdt.c		\
 			drivers/renesas/common/rom/rom_api.c		\
 			drivers/io/io_storage.c