lustre: Fix space required before the open parenthesis in mgc_required.c

This patch fixed "ERROR: space required before the open
parenthesis'('" found by checkpatch.pl in
lustre/lustre/mgc/mgc_request.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>