dt-bindings: serial: snps,dw-apb-uart: merge duplicate compatible entry.

dt-bindings: serial: snps,dw-apb-uart: merge duplicate compatible entry.

Each vendor have an items entry of its own compatible, It is needless
and can be merged as it share the same base "snps,dw-apb-uart"
compatible.

Merge the duplicate compatible entry into one item entry.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Suggested-by: Conor Dooley <conor@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20241024062105.782330-2-inochiama@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>