staging: exfat: make exfat depend on BLOCK

This should fix a build error in some configurations when CONFIG_BLOCK
is not selected.  Also properly set the dependancy for no FAT support at
the same time.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Link: https://lore.kernel.org/r/20190902174631.GB31445@kroah.com
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/exfat/Kconfig

 config EXFAT_FS
 	tristate "exFAT fs support"
+	depends on BLOCK
 	select NLS
 	help
 	  This adds support for the exFAT file system.
 
 config EXFAT_DONT_MOUNT_VFAT
 	bool "Prohibit mounting of fat/vfat filesysems by exFAT"
+	depends on EXFAT_FS
 	default y
 	help
 	  By default, the exFAT driver will only mount exFAT filesystems, and refuse