drm/i915/perf: Reverse a ternary to make sparse happy

Avoid

drivers/gpu/drm/i915/i915_perf.c:2442:85: warning: dubious: x | !y

simply by inverting the predicate and reversing the ternary.

v2: Move the long lines into their own function so there is no confusion
on operator precedence.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191101192116.12647-1-chris@chris-wilson.co.uk