dt-bindings: PCI: mediatek-gen3: Add support for MT6991/MT8196

dt-bindings: PCI: mediatek-gen3: Add support for MT6991/MT8196

Add compatible strings for MT8196 and MT6991 (which are fully
compatible between each other) and clock definitions.

These new SoCs don't have tl_96m and tl_32k clocks, but need
an AHB to APB bus clock and a low power clock.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
[mani: changed 'maxItems' to 'minItems' for reset]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250703120847.121826-3-angelogioacchino.delregno@collabora.com