ARM: dts: armada-xp-98dx3236: Switch to armada-38x-uart serial node

Switch to the "marvell,armada-38x-uart" driver variant to empty
the UART buffer before writing to the UART_LCR register.

Signed-off-by: Joshua Scott <joshua.scott@alliedtelesis.co.nz>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Gregory CLEMENT <gregory.clement@bootlin.com&gt;.>
Cc: stable@vger.kernel.org
Fixes: 43e28ba8 ("ARM: dts: Use armada-370-xp as a base for armada-xp-98dx3236")
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>