ice: ensure the copied buf is NUL terminated

In the Linux kernel, the following vulnerability has been resolved:

ice: ensure the copied buf is NUL terminated

Currently, we allocate a count-sized kernel buffer and copy count bytes

from userspace to that buffer. Later, we use sscanf on this buffer but we

don't ensure that the string is terminated inside the buffer, this can lead

to OOB read when using sscanf. Fix this issue by using memdup_user_nul

instead of memdup_user.