dts: add Qualcomm rbx boards

Add initial support for the RB1, RB2, and RB5 Robotice Platforms.

These boards are based on the QCM2290, SM6115, and SM8250 SoC
respectively.

Initial support includes:
 * Internal MMC on RB1 and RB2
 * USB host mode on all boards
 * SDHCI card support on all boards

These boards, like the Dragonboard845c, rely on the first-stage EDK2
based bootloader to chainload u-boot.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
4 files changed