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>

cmd/Kconfig

@@ -517,7 +517,7 @@ config CMD_SPL
 config CMD_SPL_NAND_OFS
 	hex "Offset of OS args or dtb for Falcon-mode NAND boot"
 	depends on CMD_SPL && (TPL_NAND_SUPPORT || SPL_NAND_SUPPORT)
-	default 0
+	default 0x0
 	help
 	  This provides the offset of the command line arguments for Linux
 	  when booting from NAND in Falcon mode.  See doc/README.falcon
@@ -527,7 +527,7 @@ config CMD_SPL_NAND_OFS
 config CMD_SPL_NOR_OFS
 	hex "Offset of OS args or dtb for Falcon-mode NOR boot"
 	depends on CMD_SPL && SPL_NOR_SUPPORT
-	default 0
+	default 0x0
 	help
 	  This provides the offset of the command line arguments or dtb for
 	  Linux when booting from NOR in Falcon mode.
@@ -1514,7 +1514,7 @@ config DEFAULT_SPI_BUS
 config DEFAULT_SPI_MODE
 	hex "default spi mode used by sspi command (see include/spi.h)"
 	depends on CMD_SPI
-	default 0
+	default 0x0
 
 config CMD_TEMPERATURE
 	bool "temperature - display the temperature from thermal sensors"
@@ -1805,7 +1805,7 @@ config BOOTP_PXE_CLIENTARCH
 	depends on BOOTP_PXE
 	default 0x16 if ARM64
 	default 0x15 if ARM
-	default 0 if X86
+	default 0x0 if X86
 
 config BOOTP_VCI_STRING
 	string