LoongArch: Delete unnecessary debugfs checking

mainline inclusion
from mainline-v6.5-rc1
commit d7c24960
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MWTU


CVE: NA

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

Debugfs functions are not supposed to be checked for errors.  This
is sort of unusual but it is described in the comments for the
debugfs_create_dir() function.  Also debugfs_create_dir() can never
return NULL.

Signed-off-by: Yongzhen Zhang <zhangyongzhen@kylinos.cn>
Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>