toaster: Fix broken overrides usage

This fixes data corruption issues with toaster where image data wasn't
being processed correct.

(From OE-Core rev: fbbb689c8df7f82644b8a9bc5bb6884bc6516660)

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

meta/classes/toaster.bbclass

@@ -101,12 +101,12 @@ def _toaster_load_pkgdatafile(dirpath, filepath):
         for line in fin:
             try:
                 kn, kv = line.strip().split(": ", 1)
-                m = re.match(r"^PKG_([^A-Z:]*)", kn)
+                m = re.match(r"^PKG:([^A-Z:]*)", kn)
                 if m:
                     pkgdata['OPKGN'] = m.group(1)
-                kn = "_".join([x for x in kn.split("_") if x.isupper()])
-                pkgdata[kn] = kv.strip()
-                if kn == 'FILES_INFO':
+                kn = kn.split(":")[0]
+                pkgdata[kn] = kv
+                if kn.startswith('FILES_INFO'):
                     pkgdata[kn] = json.loads(kv)
 
             except ValueError: