Add space after PACKAGECONFIG append

All of the package configs in lower layers currently dont have spaces before. The ideal approach here is to prepend a whitespace before each PACKAGECONFIG append but to mitigate the issue for now, we will add an extra whitespace after this PACAKGEAPPEND.

Lower layers have
PACKAGECONFIG:append = "gbmcweb-platform-plugins"

This will cause PACKAGECONFIG parsing failures during build.

Tested:
Bitbake correctly parses configs.
- Platform11:
  - http://fusion2/43ed2ef4-c384-31ee-8987-1a3aee40f010
  - http://fusion2/641b0e16-e254-372f-95ff-bef0c7c82acd
- Platform5: http://fusion2/3b08e71d-029f-3a13-9ad5-b8b891746bcd
- Platform15: http://fusion2/92228b98-039a-30bc-a744-5f1d2b3e104e
- Platform17: http://fusion2/42ebece9-219f-3911-bf18-e13012dd8794
Google-Bug-Id: 467748392
Change-Id: I150302131d8ab7ec0dbe6c8472225afe95d02f41
Signed-off-by: Edward Lee <edwarddl@google.com>