net: emaclite: Let's make xemaclite_adjust_link static

xemaclite_adjust_link is used locally.
It removes sparse warning:
drivers/net/ethernet/xilinx/xilinx_emaclite.c:916:6: warning:
symbol 'xemaclite_adjust_link' was not declared. Should it be static?

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>