clk: pistachio: Declare mux table as const u32[]

Now that clk_register_mux_table takes a const u32 *, we can declare the
mux table as const u32[].

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20220205103613.1216218-8-j.neuschaefer@gmx.net


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