net: phy: linux/phy.h: fix Excess kernel-doc description warning

Remove the @phy_timer: line to prevent the kernel-doc warning:

include/linux/phy.h:768: warning: Excess struct member 'phy_timer' description in 'phy_device'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: netdev@vger.kernel.org
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>