smb: client: use GFP_KERNEL for DFS cache allocations

smb: client: use GFP_KERNEL for DFS cache allocations

In dfs_cache.c, the helper functions alloc_target(), setup_referral(),
and update_cache_entry_locked() currently utilize GFP_ATOMIC to
allocate memory.

However, all of these functions are executed in sleepable conditions.
Use GFP_KERNEL instead, to reduce the risk of allocation failure and
stop putting unnecessary pressure on emergency memory pools in
low-memory scenarios.

Signed-off-by: Fredric Cover <fredric.cover.lkernel@gmail.com>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Steve French <stfrench@microsoft.com>