arm64: dts: rockchip: Add I2S2 node for RADXA Rock 3A

This patch adds I2S2 node for Radxa Rock 3A's M.2 E key slot for
Bluetooth PCM input. I2S2 is not used now, but could be configured
for Bluetooth HFP over PCM in future patches.

Signed-off-by: Shengyu Qu <wiagn233@outlook.com>
Link: https://lore.kernel.org/r/OS3P286MB259791E603F96942F51332D098359@OS3P286MB2597.JPNP286.PROD.OUTLOOK.COM


Signed-off-by: Heiko Stuebner <heiko@sntech.de>