fs: Kconfig: Add a separate config for FS_CBFS

Rather than using CMD_CBFS for both the filesystem and its command, we
should have a separate option for each. This allows us to enable CBFS
support without the command, if desired, which reduces U-Boot's size
slightly.

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: imply FS_CBFS on SYS_COREBOOT]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 8a16ed7..7a12441 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -882,6 +882,7 @@
 menu "Filesystem commands"
 config CMD_CBFS
 	bool "Enable the 'cbfs' command"
+	depends on FS_CBFS
 	help
 	  Define this to enable support for reading from a Coreboot
 	  filesystem. This is a ROM-based filesystem used for accessing files