phy: rk-inno-usb2: Decrease verbosity of repeating log.

phy-rockchip-inno-usb2 logs the message

  "phy-ff2c0000.syscon:usb2-phy@100.2: charger = INVALID_CHARGER"

constantly with a frequency of about 1 Hz and a verbosity level
of INFO. As this is clearly annoying, this patch decreases
the log level to DEBUG.

Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>