perf report: Do not collect sample histogram unnecessarily

The data type profiling alone doesn't need the sample histogram for
functions.  It only needs the histogram for the types.

Let's remove the condition in the report_callback to check if data type
profiling is selected and make sure the annotation has the 'struct
annotated_source' instantiated before calling symbol__disassemble().

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>