smb: client: change allocation requirements in DUP_CTX_STR macro

smb: client: change allocation requirements in DUP_CTX_STR macro

Currently, the macro DUP_CTX_STR allocates new_ctx->field using
GFP_ATOMIC. DUP_CTX_STR is only used in smb3_fs_context_dup(), which
is never called in an atomic context. Using GFP_ATOMIC puts unnecessary
pressure on emergency memory pools.

Change GFP_ATOMIC to GFP_KERNEL.

Signed-off-by: Fredric Cover <fredric.cover.lkernel@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>