phy: cadence: Sierra: Constify static structs

The static cdns_reg_pairs and regmap_config structs are not modified and
can be made const. This allows the compiler to put them in read-only
memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20200912204639.501669-2-rikard.falkeborn@gmail.com


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