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/arch/arm/mach-rockchip/Kconfig b/arch/arm/mach-rockchip/Kconfig
index 49da93d..4569a9c 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -469,7 +469,7 @@
 
 config ROCKCHIP_SPL_RESERVE_IRAM
 	hex "Size of IRAM reserved in SPL"
-	default 0
+	default 0x0
 	help
 	  SPL may need reserve memory for firmware loaded by SPL, whose load
 	  address is in IRAM and may overlay with SPL text area if not