usb: phy: ab8500: remove unused ab8500_eyediagram_workaroud()

The only caller of this function is gone, so now we get a warning:

drivers/usb/phy/phy-ab8500-usb.c:1026:17: error: 'ab8500_eyediagram_workaroud' defined but not used [-Werror=unused-function]

It is possible that we should in fact still call the function from
somewhere else, but I don't see from where.

Fixes: 635f997a499b ("usb: phy: ab8500: Remove the set_power callback")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>