staging: lustre: rename proc_call_handler to lprocfs_call_handler

Using proc_call_handler as a function name is way too generic.
Rename to lprocfs_call_handler to avoid possible collisions.

Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>