perf hist: Fix memory leak of srcline

We can't allocate he->srcline unconditionaly, only when new hist_entry
is created. Moving he->srcline allocation into hist_entry__init
function.

Original-patch-by: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Nageswara R Sastry <nasastry@in.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Link: http://lkml.kernel.org/r/20190305152536.21035-4-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>