usb: host: dwc3: fix phys init

When no PHYs are declared in the dwc3 node, the phy init fails.
This patch checks if the "phys" property is presend and reports
the error returned by dev_count_phandle_with_args().

This patchs also fixes the styles issues added in last commit.

This patch should fix the DWC3 support on the UniPhier SoC family.

Fixes: 7c839ea7 ("usb: host: dwc3: Add support for multiple PHYs")
Reported-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>