clk: samsung: Add bindings for 32kHz clocks from s2mps11

This creates include/dt-bindings/clock/samsung,s2mps11.h with
the three 32kHz clock outputs from the s2mps11 mfd.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>