Staging: lustre: Replace __FUNCTION__ with __func__

This patch fixes the following checkpatch.pl warning in lustre/ldlm/ldlm_request.c-
WARNING: __func__ should be used instead of gcc specific __FUNCTION__

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>