blackfin: Move blackfin watchdog driver out of the blackfin arch folder.

- Enable hw_watchdog_init() in watchdog.h if CONFIG_HW_WATCHDOG is defined.
- Move blackfin hw watchdog driver to the generic driver folder.
- Call hw_watchdog_init() from blackfin board init code.
- Reuse macro CONFIG_WATCHDOG_TIMEOUT_MSECS
- Update README.watchdog accordingly

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>

drivers/watchdog/Makefile

@@ -33,6 +33,7 @@ endif
 COBJS-$(CONFIG_TNETV107X_WATCHDOG) += tnetv107x_wdt.o
 COBJS-$(CONFIG_S5P)               += s5p_wdt.o
 COBJS-$(CONFIG_XILINX_TB_WATCHDOG) += xilinx_tb_wdt.o
+COBJS-$(CONFIG_BFIN_WATCHDOG)  += bfin_wdt.o
 
 COBJS	:= $(COBJS-y)
 SRCS	:= $(COBJS:.o=.c)

drivers/watchdog/bfin_wdt.c

@@ -0,0 +1,26 @@
+/*
+ * watchdog.c - driver for Blackfin on-chip watchdog
+ *
+ * Copyright (c) 2007-2009 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <common.h>
+#include <watchdog.h>
+#include <asm/blackfin.h>
+#include <asm/mach-common/bits/watchdog.h>
+
+void hw_watchdog_reset(void)
+{
+	bfin_write_WDOG_STAT(0);
+}
+
+void hw_watchdog_init(void)
+{
+	bfin_write_WDOG_CTL(WDDIS);
+	SSYNC();
+	bfin_write_WDOG_CNT(CONFIG_WATCHDOG_TIMEOUT_MSECS / 1000 * get_sclk());
+	hw_watchdog_reset();
+	bfin_write_WDOG_CTL(WDEN);
+}