net: phy: rename Asix Electronics PHY driver

[Resent to net instead of net-next - may clash with Anders Roxell's patch
series addressing duplicate module names]

Commit 31dd83b9

 ("net-next: phy: new Asix Electronics PHY driver")
introduced a new PHY driver drivers/net/phy/asix.c that causes a module
name conflict with a pre-existiting driver (drivers/net/usb/asix.c).

The PHY driver is used by the X-Surf 100 ethernet card driver, and loaded
by that driver via its PHY ID. A rename of the driver looks unproblematic.

Rename PHY driver to ax88796b.c in order to resolve name conflict.

Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Fixes: 31dd83b9

 ("net-next: phy: new Asix Electronics PHY driver")
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>