perf script: Fix compiler warning in builtin_script.c:is_top_script()

Fix annoying compiler warning in the is_top_script() function.

The issue was that a const char * was cast into a char * to call
ends_with(). We fix the users of ends_with() instead. Some are passing a
char *, but it is okay to cast the return value of ends_with() to char *
(because we understand what ends_with() does).

Cc: David S. Miller <davem@davemloft.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Stephane Eranian <eranian@gmail.com>
LKML-Reference: <4cf92096.17edd80a.1540.5d60@mx.google.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>