arm64/perf: Add PERF_ATTACH_TASK_DATA to events with has_branch_stack()

Short running processes i.e those getting very small cpu run time each time
when they get scheduled on, might not accumulate much branch records before
a PMU IRQ really happens. This increases possibility, for such processes to
loose much of its branch records, while being scheduled in-out of various
cpus on the system.

There is a need to save all occurred branch records during the cpu run time
while the process gets scheduled out. It requires an event context specific
buffer for such storage.

This adds PERF_ATTACH_TASK_DATA flag unconditionally, for all branch stack
sampling events, which would allocate task_ctx_data during its event init.
This also creates a platform specific task_ctx_data kmem cache which will
serve such allocation requests.

This adds a new structure 'arm64_perf_task_context' which encapsulates brbe
register set for maximum possible BRBE entries on the HW along with a valid
records tracking element.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>