phy: tegra: Constify static device_type structs

phy: tegra: Constify static device_type structs

The only usage of tegra_xusb_pad_type and tegra_xusb_port_type is to
assign their address to the type field in the device struct, which is a
const pointer. Make them const to allow the compiler to put them in
read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20201109215844.167954-1-rikard.falkeborn@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>