usb: gadget: mv_udc_core: fix phy_regs I/O memory leak

There was an omission in transition to devm_xxx resource handling.
iounmap(udc->phy_regs) were removed, but ioremap() was left
without devm_.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Fixes: 3517c31a ("usb: gadget: mv_udc: use devm_xxx for probe")
Signed-off-by: Felipe Balbi <balbi@ti.com>