arm: socfpga: Add watchdog disable for socfpga

This adds watchdog disable. It is neccessary for running Linux kernel.

Signed-off-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Pavel Machek <pavel@denx.de>

V2: Move RSTMGR_PERMODRST_L4WD0_LSB to reset_manager.h
    Reset watchdog only if CONFIG_HW_WATCHDOG is undefined (the default)
diff --git a/arch/arm/cpu/armv7/socfpga/reset_manager.c b/arch/arm/cpu/armv7/socfpga/reset_manager.c
index e320c01..5d7aba4 100644
--- a/arch/arm/cpu/armv7/socfpga/reset_manager.c
+++ b/arch/arm/cpu/armv7/socfpga/reset_manager.c
@@ -14,6 +14,18 @@
 static const struct socfpga_reset_manager *reset_manager_base =
 		(void *)SOCFPGA_RSTMGR_ADDRESS;
 
+/* Toggle reset signal to watchdog (WDT is disabled after this operation!) */
+void socfpga_watchdog_reset(void)
+{
+	/* assert reset for watchdog */
+	setbits_le32(&reset_manager_base->per_mod_reset,
+		     1 << RSTMGR_PERMODRST_L4WD0_LSB);
+
+	/* deassert watchdog from reset (watchdog in not running state) */
+	clrbits_le32(&reset_manager_base->per_mod_reset,
+		     1 << RSTMGR_PERMODRST_L4WD0_LSB);
+}
+
 /*
  * Write the reset manager register to cause reset
  */