smart_grid: introduce smart_grid cmdline

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8WMOG


CVE: NA

----------------------------------------

We need a cmdline to decide whether smart_grid is enabled.

Need to add "smart_grid" string in kernel boot cmdline, if we want
to enable the feature.

Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>