ARM: dts: imx6ul: Drop dma-apb interrupt-names

Drop "interrupt-names" property, since it is broken. The drivers/dma/mxs-dma.c
in Linux kernel does not use it, the property contains duplicate array entries
in existing DTs, and even malformed entries (gmpi, should have been gpmi). Get
rid of that optional property altogether.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>