CLK: HSDK: CGU: support PLL bypassing

Support setting PLL to bypass mode to support output frequency
equal to input one.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Link: https://lkml.kernel.org/r/20200311134115.13257-3-Eugeniy.Paltsev@synopsys.com


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