phy: amlogic: meson8b-usb2: Use a MMIO regmap

Using a MMIO regmap and switch to regmap_update_bits() to simplify the
code in the driver. Also switch to devm_platform_ioremap_resource()
instead of open-coding it. No functional changes intended.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Thomas Graichen <thomas.graichen@gmail.com>
Link: https://lore.kernel.org/r/20200512222424.549351-4-martin.blumenstingl@googlemail.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>