recordmcount.pl: Add support for __fentry__

recordmcount.pl: Add support for __fentry__

With gcc 4.6.0 the -mfentry feature places the function profiling call
at the start of the function. When this is used, the call is to
__fentry__ and not mcount.  This is required for Ksplice as the C
version of recordmcount doesn't insert section symbols for the
__mcount_loc section so we fall back to the perl version.

Based on 48bb5dc6cd9d30fe0d594947563da1f8bd9abada (ftrace: Make
recordmcount.c handle __fentry__).
Link: http://lkml.kernel.org/r/1383648129-10724-1-git-send-email-jamie.iles@oracle.com
Signed-off-by: Jamie Iles <jamie.iles@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>