axs101: fix dw gmac instantiation for updated dw gmac driver

With accepted change to DW GMAC driver -
92a190aa (net/designware - switch driver
to phylib usage) we need to update this board because
"designware_initialize" now accepts only 2 parameters instead of 4.

Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Tom Rini <trini@ti.com>

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>