x86/spec-ctrl: Fix default calculation of opt_srb_lock
Since this logic was introduced, opt_tsx has become more complicated and
shouldn't be compared to 0 directly. While there are no buggy logic paths,
the correct expression is !(opt_tsx & 1) but the rtm_disabled boolean is
easier and clearer to use.
Fixes: 8fe24090d940 ("x86/cpuid: Rework HLE and RTM handling") Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>