soc: sifive: ccache: define the macro for the register shifts

Define the macro for the register shifts, it could make the code be
more readable

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220913061817.22564-7-zong.li@sifive.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>