arm64/perf: Add BRBE driver

This adds a BRBE driver which implements all the required helper functions
for struct arm_pmu. Following functions are defined by this driver which
will configure, enable, capture, reset and disable BRBE buffer HW as and
when requested via perf branch stack sampling framework.

- arm64_pmu_brbe_filter()
- arm64_pmu_brbe_enable()
- arm64_pmu_brbe_disable()
- arm64_pmu_brbe_read()
- arm64_pmu_brbe_probe()
- arm64_pmu_brbe_reset()
- arm64_pmu_brbe_supported()

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-perf-users@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>