perf dwarf-aux: Add die_get_pointer_type to get pointer types

perf dwarf-aux: Add die_get_pointer_type to get pointer types

When a variable type is wrapped in typedef/qualifiers, callers may need
to first resolve it to the underlying DW_TAG_pointer_type or
DW_TAG_array_type. A simple tag check is not enough and directly calling
__die_get_real_type() can stop at the pointer type (e.g. typedef ->
pointer) instead of the pointee type.

Add die_get_pointer_type() helper that follows typedef/qualifier chains
and returns the underlying pointer DIE. Use it in annotate-data.c so
pointer checks and dereference work correctly for typedef'd pointers.

Signed-off-by: Zecheng Li <zli94@ncsu.edu>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>