staging: lustre: Move proc_*() functions inside #ifdef CONFIG_SYSCTL

If CONFIG_SYSCTL=n:

    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:84: warning: ‘proc_set_timeout’ defined but not used
    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:95: warning: ‘proc_memory_alloc’ defined but not used
    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:119: warning: ‘proc_pages_alloc’ defined but not used
    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:143: warning: ‘proc_mem_max’ defined but not used
    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:167: warning: ‘proc_pages_max’ defined but not used
    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:191: warning: ‘proc_max_dirty_pages_in_mb’ defined but not used
    drivers/staging/lustre/lustre/obdclass/linux/linux-sysctl.c:232: warning: ‘proc_alloc_fail_rate’ defined but not used

Make the existing #ifdef CONFIG_SYSCTL cover all sysctl-related
functions to fix this.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>