ASoC: dt-bindings: renesas,fsi: add support multiple clocks

ASoC: dt-bindings: renesas,fsi: add support multiple clocks

The FSI on r8a7740 requires the SPU bus/bridge clock to be enabled before
accessing its registers. Without this clock, any register access leads to
a system hang as the FSI block sits behind the SPU bus.
Update the binding to support multiple clocks to properly describe the
hardware clock tree, including:
  - SPU bus/bridge clock (spu) for register access.
  - CPG DIV6 clocks (icka/b) as functional clock.
  - FSI dividers (diva/b) for audio clock generation.
  - External clock inputs (xcka/b) provided by the board.
The hardware supports several valid clock configurations. For example,
when both FSIA and FSIB operate as slaves, only the fck and spu clocks
are required. When a port operates as a master, it can use either an
internal clock source (ickx + divx) or an external clock source
(ickx + xckx). Therefore, while fck and spu are mandatory on r8a7740,
the remaining clocks (icka/b, diva/b and xcka/b) are optional and depend
on the selected master/slave configuration and clock source.
Both sh73a0 and r8a7740 define the SPU DIV6 clock control register at
0xe6150084. The binding therefore documents the clocks supported by the
FSI driver for these variants.

Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260609113836.45079-2-phucduc.bui@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>