bgmac: Update fixed_phy_register()

Commit a5597008 ("phy: fixed_phy: Add gpio to determine link up/down.")
added a new argument to fixed_phy_register(), but missed to update bgmac
driver, causing the following build failure:

drivers/net/ethernet/broadcom/bgmac.c:1450:2: error: too few arguments to function 'fixed_phy_register'

Add the missing argument.

Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>