Add mtd-utils dependency if cfi or ubivol are set

This fixes the build issue below when CONFIG_CFI or CONFIG_UBIVOL are
set but CONFIG_MTD is not.

	| In file included from handlers/flash_handler.c:44:0:
	| include/flash.h:26:24: fatal error: mtd/libmtd.h: No such file or directory
	|  #include <mtd/libmtd.h>

Signed-off-by: Gaël PORTAY <gael.portay@savoirfairelinux.com>

recipes-support/swupdate/swupdate.inc

@@ -75,6 +75,13 @@ python () {
         depends = d.getVar('DEPENDS', False)
         d.setVar('DEPENDS', depends + ' mtd-utils')
 
+    if 'CONFIG_CFI=y\n' in features:
+        depends = d.getVar('DEPENDS', False)
+        d.setVar('DEPENDS', depends + ' mtd-utils')
+
+    if 'CONFIG_UBIVOL=y\n' in features:
+        depends = d.getVar('DEPENDS', False)
+        d.setVar('DEPENDS', depends + ' mtd-utils')
 }
 
 do_configure () {