cifs: Provide the capability to extract from ITER_FOLIOQ to RDMA SGEs

Make smb_extract_iter_to_rdma() extract page fragments from an ITER_FOLIOQ
iterator into RDMA SGEs.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Tom Talpey <tom@talpey.com>
cc: Enzo Matsumiya <ematsumiya@suse.de>
cc: linux-cifs@vger.kernel.org
Link: https://lore.kernel.org/r/20240814203850.2240469-15-dhowells@redhat.com/

 # v2
Signed-off-by: Christian Brauner <brauner@kernel.org>