Fix gcc '-Wunused-but-set-variable' warning:
drivers/power/reset/ltc2952-poweroff.c:97:16: warning: variable
‘overruns’ set but not used [-Wunused-but-set-variable]
  unsigned long overruns;
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NHongbo Yao <yaohongbo@huawei.com>
Signed-off-by: NSebastian Reichel <sebastian.reichel@collabora.com>