watchdog: mpc8xx_wdt: Watchdog driver and macros cleanup

With the generic watchdog driver now implemented, this patch removes
some legacy stuff from the MPC8xx watchdog driver and its Kconfig
integration. CONFIG_MPC8xx_WATCHDOG is completely removed and
hw_watchdog_reset() is made static, as the watchdog will now get
serviced via the DM infrastructure if enabled via CONFIG_WATCHDOG.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c727d91..0b1629b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -35,7 +35,7 @@
 	bool "MPC8xx"
 	select BOARD_EARLY_INIT_F
 	imply CMD_REGINFO
-	imply MPC8xx_WATCHDOG
+	imply WDT_MPC8xx
 
 endchoice