ARM: dts: da850: Add ti,da830-uart compatible for serial ports

TI DA8xx/OMAPL13x/AM17xx/AM18xx SoCs have extra UART registers beyond
the standard 8250 registers, so we need a new compatible string to
indicate this. Also, at least one of these registers uses the full 32
bits, so we need to specify reg-io-width in addition to reg-shift.

"ns16550a" is left in the compatible specification since it does work
as long as the bootloader configures the SoC UART power management
registers.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>