packagegroups: LIC_FILES_CHKSUM not needed for PGs

Defining LIC_FILES_CHKSUM is not needed for packagegroups anymore.

Signed-off-by: Fahad Usman <fahad_usman@mentor.com>
Merge pull request #273 from fahadusman/remove-unnecessary-bits

packagegroups: LIC_FILES_CHKSUM not needed for PGs