clk: ingenic: Use CLK_OF_DECLARE_DRIVER macro

By using CLK_OF_DECLARE_DRIVER instead of the CLK_OF_DECLARE macro, we
allow the driver to probe also as a platform driver.

While this driver does not have code to probe as a platform driver, this
is still useful for probing children devices in the case where the
device node is compatible with "simple-mfd".

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lkml.kernel.org/r/20190810123620.27238-1-paul@crapouillou.net
Signed-off-by: Stephen Boyd <sboyd@kernel.org>