ARM: dts: omap2/3: Drop dmas property from I2C node

DMA was never supported by i2c-omap driver and the bindings were never
documented. Therefore drop the entries in preparation to moving
bindings to YAML schema.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>