apparmor: Modify mismatched function name

No functional modification involved.

security/apparmor/lib.c:93: warning: expecting prototype for aa_mask_to_str(). Prototype was for val_mask_to_str() instead.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=13606


Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>