phy: allwinner: phy-sun6i-mipi-dphy: Constify structs

sun6i_dphy_ops and sun6i_dphy_regmap_config are not modified so make them
const structs to allow the compiler to put them in read-only memory.

Before:
   text    data     bss     dec     hex filename
   4407    1944      64    6415    190f drivers/phy/allwinner/phy-sun6i-mipi-dphy.o

After:
   text    data     bss     dec     hex filename
   4835    1496      64    6395    18fb drivers/phy/allwinner/phy-sun6i-mipi-dphy.o

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20200629195727.9717-1-rikard.falkeborn@gmail.com


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