drivers: wifi: esp_at: do not connect socket on bind(INADDR_ANY)

All connect() syscalls result in EISCONN error, since underlying
_sock_connect() is attempted to be called twice. Once from net_context.c'
bind_default() (with INADDR_ANY) as part of esp_bind() and second time as
part of esp_connect().

Do not call _sock_connect() from esp_bind(INADDR_ANY), which happens as
part of connect().

Fixes: dbf3d6e9 ("drivers: esp_at: implement bind() and recvfrom() for
  UDP sockets")
Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>