sanity: make license QA failures fatal again

sanity: make license QA failures fatal again

Previous work to clean up the license QA code (oe-core fbdf977) had the side
effect that failing the license sanity check (bad or missing LIC_FILES_CHKSUM)
would emit an error message but wouldn't actually abort the build.

Solve this by changing populate_lic_qa_checksum() so that it tracks if the
message class was in ERROR_QA and if so, aborts the function.

[ YOCTO #10280 ]

(From OE-Core rev: 5ba1a7505b904a4aa2118fa9614d76df97597af8)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>