clk: Support bypassing dividers

When a clock is declared as both CGU_CLK_DIV and CGU_CLK_MUX, the CGU
code expects the mux to be applied first, the divider second.

On the JZ4760, and maybe on some other SoCs, some clocks also have a mux
setting and a divider, but the divider is not applied to all parents
selectable from the mux.

This could be solved by creating two clocks, one with CGU_CLK_DIV and
one with CGU_CLK_MUX, but that would increase the number of clocks.

Instead, add a 8-bit mask to CGU_CLK_DIV clocks. If the bit
corresponding to the parent clock's index is set, the divider is
bypassed.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20210530164923.18134-3-paul@crapouillou.net
Signed-off-by: Stephen Boyd <sboyd@kernel.org>