usb: phy: msm-hsusb: Use device tree reg-names property

In preparation for adding more optional IO registers, change the
driver to call the platform_get_resource_byname() variant.
This will allow more flexibility of specifying registers in
device tree by requiring the "reg-names" rather than error-prone
index-based lookup.

Change-Id: I073ca90936ea2968e6071ec8518a6556fba40ee3
Signed-off-by: Jack Pham <jackp@codeaurora.org>