dt-bindings: serial: pl011: Add a reg-io-width parameter

Some of the implementations support only 32-bit accesses.
Add a parameter reg-io-width for such platforms.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Link: https://lore.kernel.org/r/20220826120559.2122-2-shubhrajyoti.datta@amd.com


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