clk: mvebu: armada-37xx-periph: add suspend/resume support

Add suspend/resume hooks in Armada 37xx peripheral clocks driver to
handle S2RAM operations.

One can think that these hooks are useless by comparing the register
values before and after a suspend/resume cycle: they will look the same
anyway. This is because of some scripts executed by the Cortex-M3 core
during ATF operations to init both the clocks and the DDR. These values
could be modified by the BL33 stage or by Linux itself and should be
preserved.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>