arm64: renesas: Split R-Car Gen3 and Gen4 common board code

Split common board code for R-Car Gen3 and Gen4 into separate files.
The R-Car Gen3 board code contains fixups specific to TFA which are
no longer required on R-Car Gen4, keep those fixups in its own file
so they would not interfere with Gen4.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/board/renesas/rcar-common/gen4-common.c b/board/renesas/rcar-common/gen4-common.c
index 36a51bc..2abe966 100644
--- a/board/renesas/rcar-common/gen4-common.c
+++ b/board/renesas/rcar-common/gen4-common.c
@@ -74,3 +74,17 @@
 
 	return 0;
 }
+
+#define RST_BASE	0xE6160000 /* Domain0 */
+#define RST_SRESCR0	(RST_BASE + 0x18)
+#define RST_SPRES	0x5AA58000
+
+void __weak reset_cpu(void)
+{
+	writel(RST_SPRES, RST_SRESCR0);
+}
+
+int ft_board_setup(void *blob, struct bd_info *bd)
+{
+	return 0;
+}