platform/chrome: cros_ec: Make some symbols static

platform/chrome: cros_ec: Make some symbols static

Fix sparse warning:

drivers/platform/chrome/cros_ec_debugfs.c:256:30: warning: symbol 'cros_ec_console_log_fops' was not declared. Should it be static?
drivers/platform/chrome/cros_ec_debugfs.c:265:30: warning: symbol 'cros_ec_pdinfo_fops' was not declared. Should it be static?
drivers/platform/chrome/cros_ec_lightbar.c:550:24: warning: symbol 'cros_ec_lightbar_attr_group' was not declared. Should it be static?
drivers/platform/chrome/cros_ec_sysfs.c:338:24: warning: symbol 'cros_ec_attr_group' was not declared. Should it be static?
drivers/platform/chrome/cros_ec_vbc.c:104:24: warning: symbol 'cros_ec_vbc_attr_group' was not declared. Should it be static?
drivers/platform/chrome/cros_ec_lpc.c:408:25: warning: symbol 'cros_ec_lpc_pm_ops' was not declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>