clk: sifive: Use common name for prci configuration

Use generic name CLK_SIFIVE_PRCI instead of CLK_SIFIVE_FU540_PRCI. This
patch is prepared for fu740 support.

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Reviewed-by: Pragnesh Patel <Pragnesh.patel@sifive.com>
Link: https://lore.kernel.org/r/20201209094916.17383-3-zong.li@sifive.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>