perf expr: Fix return value of ids__new()

perf expr: Fix return value of ids__new()

callers of ids__new() function only do NULL checking for the return
value. ids__new() calles hashmap__new(), which may return
ERR_PTR(-ENOMEM).

Instead of changing the checking one-by-one return NULL instead of
ERR_PTR(-ENOMEM) to keep it consistent.

Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: German Gomez <german.gomez@arm.com>
Tested-by: German Gomez <german.gomez@arm.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20211214011030.20200-1-linmq006@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>