ARM: mvebu: add audio I2S controller to Armada 38x Device Tree

This commit adds the description of the I2S controller to the Marvell
Armada 38x SoC's Device Tree, as well as its pin configuration.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Nadav Haklai <nadavh@marvell.com>
Tested-by: Nadav Haklai <nadavh@marvell.com>
Tested-by: Lior Amsalem <alior@marvell.com>
[pali: Fix i2s-pins name]
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>