dt-bindings: serial: 8250: allow clock 'uartclk' and 'reg' for nxp,lpc1850-uart

Allow clock 'uartclk' and 'reg' for nxp,lpc1850-uart to align existed
driver and dts. It is really old platform. Keep the same restriction for
others.

Allow dmas and dma-names property, which allow maxItems 4 because very old
platform (arch/arm/boot/dts/nxp/lpc/lpc18xx.dtsi) use duplicate "tx", "rx",
"tx", "rx" as dma-names.

Fix below CHECK_DTB warnings:
  arch/arm/boot/dts/nxp/lpc/lpc4337-ciaa.dtb: serial@40081000 (nxp,lpc1850-uart): clock-names: ['uartclk', 'reg'] is too long

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Acked-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://lore.kernel.org/r/20250602142745.942568-1-Frank.Li@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>