meta: Convert IMAGE_TYPEDEP to use override syntax

The IMAGE_TYPEDEP variable would make more sense to match the form of the
other image override variables, convert it to use the overrides format.

(From OE-Core rev: 8573f6b2a7af9867da0b21936ffd2cd2a417de1d)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/image.bbclass

@@ -382,8 +382,8 @@ python () {
         if t.startswith("debugfs_"):
             t = t[8:]
             debug = "debugfs_"
-        deps = (d.getVar('IMAGE_TYPEDEP_' + t) or "").split()
-        vardeps.add('IMAGE_TYPEDEP_' + t)
+        deps = (d.getVar('IMAGE_TYPEDEP:' + t) or "").split()
+        vardeps.add('IMAGE_TYPEDEP:' + t)
         if baset not in typedeps:
             typedeps[baset] = set()
         deps = [debug + dep for dep in deps]