phy: Fix armada375 compile test build on UM

The phy-armada375-usb2 driver uses IOMEM functions so COMPILE_TEST && OF
build failed with:

drivers/built-in.o: In function `armada375_usb_phy_probe':
phy-armada375-usb2.c:(.text+0x121d): undefined reference to
`devm_ioremap_resource'

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>