Kconfigs: Correct default of "0" on hex type entries

It is not a parse error to have a default value of "0" for a "hex" type
entry, instead of "0x0".  However, "0" and "0x0" are not treated the
same even by the tools themselves. Correct this by changing the default
value from "0" to "0x0" for all hex type questions that had the
incorrect default. Fix one instance (in two configs) of a default of "0"
being used on a hex question to be "0x0". Remove the cases where a
defconfig had set a value of "0x0" to be used as the default had been
"0".

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index a1e0899..7ca42df 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -482,8 +482,8 @@
 config DEBUG_UART_BASE
 	hex "Base address of UART"
 	depends on DEBUG_UART
-	default 0 if DEBUG_SBI_CONSOLE
-	default 0 if DEBUG_UART_SANDBOX
+	default 0x0 if DEBUG_SBI_CONSOLE
+	default 0x0 if DEBUG_UART_SANDBOX
 	default 0xff000000 if DEBUG_UART_ZYNQ && ARCH_ZYNQMP
 	default 0xe0000000 if DEBUG_UART_ZYNQ && ARCH_ZYNQ
 	help
@@ -1139,6 +1139,6 @@
 config SYS_SDMR
 	hex "SDMR Value"
 	depends on MPC8XX_CONS
-	default 0
+	default 0x0
 
 endif