drivers: esp_at: implement bind() and recvfrom() for UDP sockets

Implement bind() and recvfrom() for UDP sockets. This is achived by
setting remote field in net_pkt which in return makes recvfrom() fill
in *src_addr. This is only implemented for passiv mode and CIPDINFO needs
to be enabled. Also set net_if to non-dormant when enabling AP mode to
make binding to a port and address possible.

Signed-off-by: John Johnson <john.filip.johnson@gmail.com>