wic: IMAGE_BOOT_FILES format checks in bootimg-partition source

Check for malformed entries in IMAGE_BOOT_FILES, fail early if such
entries were found.

(From OE-Core rev: e56072aaaad6cfa222853a4e9e68dd8aa861de18)

Signed-off-by: Maciej Borzecki <maciej.borzecki@open-rnd.pl>
Signed-off-by: Maciek Borzecki <maciek.borzecki@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/plugins/source/bootimg-partition.py

@@ -90,6 +90,8 @@ class BootimgPartitionPlugin(SourcePlugin):
         for src_entry in re.findall(r'[\w;\-\./]+', boot_files):
             if ';' in src_entry:
                 dst_entry = tuple(src_entry.split(';'))
+                if not dst_entry[0] or not dst_entry[1]:
+                    msger.error('Malformed boot file entry: %s' % (src_entry))
             else:
                 dst_entry = (src_entry, src_entry)