scsi: ufs: Fix compilation failure with CONFIG_LOCK_STAT

from include/linux/kobject.h:21:0,
from include/linux/device.h:17,
from include/linux/devfreq.h:16,
from drivers/scsi/ufs/ufshcd.c:42:
drivers/scsi/ufs/ufshcd.c:
	In function 'ufshcd_init_clk_gating':
drivers/scsi/ufs/ufshcd.c:1548:19:
	error: 'clk_gating' undeclared (first use in this function)
sysfs_attr_init(&clk_gating->enable_attr.attr);

Change-Id: Ie61be8bc4472cf8960dc0afc3e0683c761ea177e
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>