arm64: dts: qcom: sdm845-xiaomi-beryllium: correct compatible

Tianma FHD panel is supposed to be used with fallback compatible:

  sdm845-xiaomi-beryllium-tianma.dtb: panel@0: compatible: ['tianma,fhd-video'] is too short

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230326155753.92007-11-krzysztof.kozlowski@linaro.org