clk: sunxi-ng: add A64 compatible string

As claiming Allwinner A64 SRAM C is a prerequisite for all sub-blocks of
the A64 DE2, not only the CCU sub-block, a bus driver is then written for
enabling the access to the whole DE2 part by claiming the SRAM.

In this situation, the A64 compatible string will be just added with no
other requirments, as they're processed by the parent bus driver.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>