dt-bindings: memory: mediatek: Extend LARB_NR_MAX to 32

Extend the max larb number definition as mt8192 has larb_nr over 16.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20210111111914.22211-4-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>