aspeed: Refactor AST2500 RAM Driver and Sysreset Driver

This change switches all existing users of ast2500 Watchdog to Driver
Model based Watchdog driver.

To perform system reset Sysreset Driver uses first Watchdog device found
via uclass_first_device call. Since the system is going to be reset
anyway it does not make much difference which watchdog is used.

Instead of using Watchdog to reset itself, SDRAM driver now uses Reset
driver to do that.

These were the only users of the old Watchdog API, so that API is
removed.

This all is done in one change to avoid having to maintain dual API for
watchdog in between.

Signed-off-by: Maxim Sloyko <maxims@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-aspeed/Kconfig b/arch/arm/mach-aspeed/Kconfig
index c5b90bd..4f021ba 100644
--- a/arch/arm/mach-aspeed/Kconfig
+++ b/arch/arm/mach-aspeed/Kconfig
@@ -11,19 +11,13 @@
 
 config ASPEED_AST2500
 	bool "Support Aspeed AST2500 SoC"
+	depends on DM_RESET
 	select CPU_ARM1176
 	help
 	  The Aspeed AST2500 is a ARM-based SoC with arm1176 CPU.
 	  It is used as Board Management Controller on many server boards,
 	  which is enabled by support of LPC and eSPI peripherals.
 
-config WDT_NUM
-	int "Number of Watchdog Timers"
-	default 3 if ASPEED_AST2500
-	help
-	  The number of Watchdot Timers on a SoC.
-	  AST2500 has three WDTsk earlier versions have two or fewer.
-
 source "arch/arm/mach-aspeed/ast2500/Kconfig"
 
 endif