arm64: dts: sdm845: Remove redundant u-boot DT properties

According to u-boot DT recomendation, u-boot specific DT properties belong
to *-uboot.dtsi. Also for starqltechn board (which is the only current
consumer of sdm845.dtsi), the properties are already included in
starqltechn-uboot.dtsi, so remove corresponding redundant properties.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>