MIPS: perf: Fix build failure in XLP perf support.

MIPS: perf: Fix build failure in XLP perf support.

Commit 4be3d2f3966b9f010bb997dcab25e7af489a841e ("MIPS: perf: Add XLP
support for hardware perf.") added UNSUPPORTED_PERF_EVENT_ID which was
removed a while back.

Cc: Zi Shen Lim <zlim@netlogicmicro.com>
Cc: Jayachandran C <jchandra@broadcom.com>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Cc: John Crispin <blogic@openwrt.org>
Cc: Zi Shen Lim <zlim@netlogicmicro.com>
Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Acked-by: Jayachandran C <jchandra@broadcom.com>
Patchwork: https://patchwork.linux-mips.org/patch/4730/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>