x86/ucode-amd: fix regression from c/s 23871:503ee256fecf

x86/ucode-amd: fix regression from c/s 23871:503ee256fecf

microcode_fits() must return distinct values for the success and
no-fit-but-no-error cases, so the caller can react accordingly. Make
it return 1 in the success case, and adjust its single caller.

Also remove an impossible code path - install_equiv_cpu_table(), which
gets called prior to microcode_fits(), never leaves equiv_cpu_table
being NULL without also returning an error.

Note that this is still awaiting testing on a system where the
regression was actually observed (which also requires a new enough
microcode_ctl package). Note also that this will need to be
backported to 4.0 and 4.1 (or the broken c/s that got backported
there reverted).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Committed-by: Keir Fraser <keir@xen.org>