[PATCH] bcm43xx: Fix access to non-existent PHY registers

Fix the conditions under which we poke at the APHY registers in
bcm43xx_phy_initg() to avoid a machine check on chips where they don't
exist.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>