clk: clk-si544: Implement small frequency change support

The Si544 supports changing frequencies "on the fly" when the change is
less than 950 ppm from the current center frequency. The driver now
uses the small adjustment routine for implementing this.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>