perf tools: Move x86__is_amd_cpu() to util/env.c

perf tools: Move x86__is_amd_cpu() to util/env.c

It can be called from non-x86 platform so let's move it to the general
util directory.  Also add a new helper perf_env__is_x86_amd_cpu() so
that it can be called with an existing perf_env as well.

Reviewed-by: James Clark <james.clark@linaro.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Acked-by: Kan Liang <kan.liang@linux.intel.com>
Cc: James Clark <james.clark@arm.com>
Cc: Atish Patra <atishp@atishpatra.org>
Cc: Mingwei Zhang <mizhang@google.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20241016062359.264929-7-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>