ftrace: Build without frame pointers on Microblaze

Microblaze doesn't need/support FRAME_POINTERS in order to have a working
function tracer.

The patch remove Kconfig warning.

Warning log:
warning: (LOCKDEP && FAULT_INJECTION_STACKTRACE_FILTER && LATENCYTOP &&
FUNCTION_TRACER && KMEMCHECK) selects FRAME_POINTER which has unmet direct
dependencies (DEBUG_KERNEL && (CRIS || M68K || FRV || UML || AVR32 ||
SUPERH || BLACKFIN || MN10300) || ARCH_WANT_FRAME_POINTERS)

Signed-off-by: Michal Simek <monstr@monstr.eu>
Link: http://lkml.kernel.org/r/1301908812-8119-2-git-send-email-monstr@monstr.eu
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>