Staging: lustre: remove extern in .c file

This patch removes extern from .c file; for the variable is not used
anywhere else in the file.
In addition, it mark it static in the one file it is in
"ldlm_resource.c".

Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>