net/af_xdp: reserve fill queue before socket create

net/af_xdp: reserve fill queue before socket create

Some zero copy AF_XDP drivers eg. ice require that there are addresses
already in the fill queue before the socket is created. Otherwise you may
see log messages such as:

XSK buffer pool does not provide enough addresses to fill 2047 buffers on
Rx ring 0

This commit ensures that the addresses are available before creating the
socket, instead of after.

Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
Tested-by: Ferruh Yigit <ferruh.yigit@intel.com>