xsk: use __xsk_rcv_zc_safe for ZC multi-buffer Rx processing

Commit f620af11c27b ("xsk: avoid double checking against rx queue being
full") addressed a case in copy mode, when working with multi-buffer
xdp_buff, where we were peeking onto XSK Rx queue twice, to find out if
there is a space to produce descriptors.

Adjust ZC path to follow the same principle.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/r/20260316140557.461288-1-maciej.fijalkowski@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>