phy,phy-bcm-kona-usb2.c: Add dependency on HAS_IOMEM

On archs like S390 or um this driver cannot build nor work.
Make it depend on HAS_IOMEM to bypass build failures.

drivers/phy/phy-bcm-kona-usb2.c:114: undefined reference to `devm_ioremap_resource'

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>