* m68k: fixed extension in a_load_ref_reg. Existing code cleans only bits 16-31 when loading a 8-bit register from 16-bit reference, and leaves garbage in bits 8-15.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28256 3ad0048d-3df7-0310-abae-a5850022a9f2