perf test: Fix skipping branch stack sampling test

Commit f4a2aade ("perf tests powerpc: Fix branch stack sampling
test to include sanity check for branch filter") added a skip if certain
branch options aren't available.

But the change added both -b (--branch-any) and --branch-filter options
at the same time, which will always result in a failure on any platform
because the arguments can't be used together.

Fix this by removing -b (--branch-any) and leaving --branch-filter which
already specifies 'any'. Also add warning messages to the test and perf
tool.

Output on x86 before this fix:

   $ sudo ./perf test branch
   108: Check branch stack sampling         : Skip

After:

   $ sudo ./perf test branch
   108: Check branch stack sampling         : Ok

Fixes: f4a2aade

 ("perf tests powerpc: Fix branch stack sampling test to include sanity check for branch filter")
Signed-off-by: James Clark <james.clark@arm.com>
Tested-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Anshuman.Khandual@arm.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221028121913.745307-1-james.clark@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>