misc: sgi-xp: xp_main: make some symbols static

misc: sgi-xp: xp_main: make some symbols static

The sparse tool complains as follows:

drivers/misc/sgi-xp/xp_main.c:24:22: warning:
 symbol 'xp_dbg_name' was not declared. Should it be static?
drivers/misc/sgi-xp/xp_main.c:28:15: warning:
 symbol 'xp_dbg_subname' was not declared. Should it be static?

These symbols are not used outside of xp_main.c, so this
commit marks them static.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Link: https://lore.kernel.org/r/20210324084823.7393-1-zou_wei@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>