MIPS: perf: Split the Kconfig option CONFIG_MIPS_MT_SMP

Split the Kconfig option CONFIG_MIPS_MT_SMP into CONFIG_MIPS_MT_SMP
and CONFIG_MIPS_PERF_SHARED_TC_COUNTERS so some of the code used
for performance counters that are shared between threads can be used
for MIPS cores that are not MT_SMP.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/4108/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>