perf/x86/intel: Update the FRONTEND MSR mask on Sapphire Rapids

On Sapphire Rapids, the FRONTEND_RETIRED.MS_FLOWS event requires the
FRONTEND MSR value 0x8. However, the current FRONTEND MSR mask doesn't
support it.

Update intel_spr_extra_regs[] to support it.

Fixes: 61b985e3 ("perf/x86/intel: Add perf core PMU support for Sapphire Rapids")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1648482543-14923-2-git-send-email-kan.liang@linux.intel.com