dt-bindings: clock: rockchip,rk3588-cru: add I2S MCLK output to IO clock IDs

dt-bindings: clock: rockchip,rk3588-cru: add I2S MCLK output to IO clock IDs

Add clock identifiers for the four I2S MCLK output to IO gate clocks
on RK3588, needed by board DTS files where the codec requires MCLK
from the SoC on an external IO pin.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Daniele Briguglio <hello@superkali.me>
Tested-by: Ricardo Pardini <ricardo@pardini.net>
Link: https://patch.msgid.link/20260419-rk3588-mclk-gate-grf-v4-1-513a42dd1dcc@superkali.me
Signed-off-by: Heiko Stuebner <heiko@sntech.de>