Fix the missing __iomem attribute in sun4i_usb_phy_write()
function. This fixes the following sparse warnings:

drivers/phy/phy-sun4i-usb.c:178:39: warning: incorrect type in initializer (different address spaces)
drivers/phy/phy-sun4i-usb.c:178:39:    expected void *phyctl
drivers/phy/phy-sun4i-usb.c:178:39:    got void [noderef] <asn:2>*
drivers/phy/phy-sun4i-usb.c:185:17: warning: incorrect type in argument 2 (different address spaces)
drivers/phy/phy-sun4i-usb.c:185:17:    expected void volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:185:17:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:189:24: warning: incorrect type in argument 1 (different address spaces)
drivers/phy/phy-sun4i-usb.c:189:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:189:24:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:196:17: warning: incorrect type in argument 2 (different address spaces)
drivers/phy/phy-sun4i-usb.c:196:17:    expected void volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:196:17:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:199:24: warning: incorrect type in argument 1 (different address spaces)
drivers/phy/phy-sun4i-usb.c:199:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:199:24:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:205:17: warning: incorrect type in argument 2 (different address spaces)
drivers/phy/phy-sun4i-usb.c:205:17:    expected void volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:205:17:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:208:24: warning: incorrect type in argument 1 (different address spaces)
drivers/phy/phy-sun4i-usb.c:208:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:208:24:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:210:17: warning: incorrect type in argument 2 (different address spaces)
drivers/phy/phy-sun4i-usb.c:210:17:    expected void volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:210:17:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:212:24: warning: incorrect type in argument 1 (different address spaces)
drivers/phy/phy-sun4i-usb.c:212:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:212:24:    got void *phyctl
drivers/phy/phy-sun4i-usb.c:214:17: warning: incorrect type in argument 2 (different address spaces)
drivers/phy/phy-sun4i-usb.c:214:17:    expected void volatile [noderef] <asn:2>*addr
drivers/phy/phy-sun4i-usb.c:214:17:    got void *phyctl
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>