swupdate-common: enable do_fetch with SWU generation

The metafile sw-description must be provided to generate a SWU, and this
is done via SRC_URI. Be sure then that do_fetch is executed by deleting
the noexec flag.
Signed-off-by: Stefano Babic <sbabic@denx.de>

classes/swupdate-common.bbclass

@@ -17,6 +17,8 @@ do_swuimage[stamp-extra-info] = "${MACHINE}"
 python () {
     deps = " " + swupdate_getdepends(d)
     d.appendVarFlag('do_swuimage', 'depends', deps)
+    d.delVarFlag('do_fetch', 'noexec')
+    d.delVarFlag('do_unpack', 'noexec')
 }
 
 def swupdate_getdepends(d):