x86, microcode, AMD: Fix signedness bug in generic_load_microcode()

install_equiv_cpu_table() returns type int.  It uses negative
error codes so using an unsigned type breaks the error handling.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: open list:AMD MICROCODE UPD... <amd64-microcode@amd64.org>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
LKML-Reference: <20110218091716.GA4384@bicker>
Signed-off-by: Ingo Molnar <mingo@elte.hu>