perf tools: Fix version kernel tag

perf tools: Fix version kernel tag

Generating the version kernel tag relies on "git describe" command to
get the latest Linus kernel tag.

However, when working from clones of Linus' git we may not have the latest
tag. For example, when working on Arnaldo's acme.git, we can have this:

  $ git branch
  perf/core
  $ head -n 5 ../../Makefile  | tail -n 4
  VERSION = 5
  PATCHLEVEL = 17
  SUBLEVEL = 0
  EXTRAVERSION = -rc3
  $ git describe --abbrev=0 --match "v[0-9].[0-9]*"
  v4.13-rc5

Indeed using tags is a problem as it relies on tags being pulled from
Linus' git (and pushed to the clone).

In commit 21120bed33d224e4 ("perf tools: Fix perf version generation")
Robert introduced a change to use the kernelversion rule to generate the
kernel tag when no git tags are available.

However, as mentioned above, the tag we generate may be incorrect, so
just always use kernelversion to get the tag (apart from building perf
out of tree).

Signed-off-by: John Garry <john.garry@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <rric@kernel.org>
Link: https://lore.kernel.org/r/1645449409-158238-3-git-send-email-john.garry@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>