perf/x86/intel/uncore: Add freerunning event descriptor helper macro

perf/x86/intel/uncore: Add freerunning event descriptor helper macro

Freerunning counter events are repetitive: the event code is fixed to
0xff, the unit is always "MiB", and the scale is identical across all
counters on a given PMON unit.

Introduce a new helper macro, INTEL_UNCORE_FR_EVENT_DESC(), to populate
the event, scale, and unit descriptor triplet. This reduces duplicated
lines and improves readability.

No functional change intended.

Signed-off-by: Zide Chen <zide.chen@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://patch.msgid.link/20251231224233.113839-8-zide.chen@intel.com