perf/mem: Introduce PERF_MEM_LVLNUM_UNC

Older API PERF_MEM_LVL_UNC can be replaced by PERF_MEM_LVLNUM_UNC.

Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230725150206.184-2-ravi.bangoria@amd.com