tracing: Check absolute path of input file in recordmcount.pl

The ftrace.c file may reference the mcount function and this may interfere
with the recordmcount.pl processing. To avoid this, the code does not
process the kernel/trace/ftrace.o. But currently the check is against
a relative path. This patch modifies the check to succeed if the path
is an absolute path.

Signed-off-by: Li Hong <lihong.hi@gmail.com>
LKML-Reference: <20091028050332.GC30758@uhli>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>