misc/pvpanic: Make some symbols static

Fix sparse warnings:

drivers/misc/pvpanic/pvpanic.c:28:18: warning:
 symbol 'pvpanic_list' was not declared. Should it be static?
drivers/misc/pvpanic/pvpanic.c:29:12: warning:
 symbol 'pvpanic_lock' was not declared. Should it be static?

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20210331121706.15268-1-yuehaibing@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>