arm64: dts: qcom: qrb4210-rb2: Enable load setting on SDHCI VQMMC

The MMC core calls regulator_set_load on VQMMC, enable loadsetting to
make it effective.

Fixes: 8d58a8c0 ("arm64: dts: qcom: Add base qrb4210-rb2 board dts")
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-and-Tested-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230515-topic-rb2-bits-v1-4-a52d154a639d@linaro.org