perf/x86: Move branch classifier

Commit 3e702ff6 ("perf/x86: Add LBR software filter support for Intel
CPUs") introduces a software branch filter which complements the hardware
branch filter and adds an x86 branch classifier.

Move the branch classifier to arch/x86/events/ so that it can be utilized
by other vendors for branch record filtering.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/bae5b95470d6bd49f40954bd379f414f5afcb965.1660211399.git.sandipan.das@amd.com