ARM: dts: vf610: lpuart: Add eDMA support

Add lpuart dts node properties for eDMA support, them depend on the eDMA driver.

Signed-off-by: Yuan Yao <yao.yuan@freescale.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>