clk: Add a bypass clock for K210

This is a small driver to do a software bypass of a clock if hardware
bypass is not working. I have tried to write this in a generic fashion, so
that it could be potentially broken out of the kendryte code at some future
date. For the K210, it is used to have aclk bypass pll0 and use in0 instead
so that the CPU keeps on working.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
CC: Lukasz Majewski <lukma@denx.de>
3 files changed