Kconfig: Make CMD_SPL_NAND_OFS only available when proper memory is used

This commit makes the CMD_SPL_NAND_OFS only visible when we use NAND
memory.
Before this change it was present when only CMD_SPL was enabled (and
would stay when board with other falcon boot medium is used).
Signed-off-by: NLukasz Majewski <lukma@denx.de>

cmd/Kconfig

@@ -327,6 +327,7 @@ config CMD_SPL
 config CMD_SPL_NAND_OFS
 	hex "Offset of OS command line args for Falcon-mode NAND boot"
 	depends on CMD_SPL
+	depends on CMD_SPL && (TPL_NAND_SUPPORT || SPL_NAND_SUPPORT)
 	default 0
 	help
 	  This provides the offset of the command line arguments for Linux