usb: gadget: f_mass_storage: fix mass storage dependency

Legacy gadgets supporting mass storage (g_mass_storage, g_acm_ms, g_multi)
all depend on BLOCK.

Make the standalone compilation of f_mass_storage (without any legacy
gadget) dependent no BLOCK, too.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/Kconfig

@@ -682,6 +682,7 @@ config USB_CONFIGFS_PHONET
 config USB_CONFIGFS_MASS_STORAGE
 	boolean "Mass storage"
 	depends on USB_CONFIGFS
+	depends on BLOCK
 	select USB_F_MASS_STORAGE
 	help
 	  The Mass Storage Gadget acts as a USB Mass Storage disk drive.