phy: ti: am654-serdes: Constify regmap_config

regmap_config is not modified and can be made static to allow the compiler
to put it in read-only memory.

Before:
text data bss dec hex filename
12328 3644 64 16036 3ea4 drivers/phy/ti/phy-am654-serdes.o

After:
text data bss dec hex filename
12648 3324 64 16036 3ea4 drivers/phy/ti/phy-am654-serdes.o

Signed-off-by: Rikard Falkeborn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/phy/ti/phy-am654-serdes.c

···
 #define to_serdes_am654_clk_mux(_hw)	\
 		container_of(_hw, struct serdes_am654_clk_mux, hw)
 
-static struct regmap_config serdes_am654_regmap_config = {
+static const struct regmap_config serdes_am654_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
 	.reg_stride = 4,