ARM: dts: msm: Add external 5V boost support for SDM845

In SDM845 with MID-MID configuration, the external 5V boost in SEM1355
is controlled via PMI8998 GPIO10. Expose it as a fixed regulator.

Remove smb2_vbus node, not used in SDM845 platforms.

Change-Id: Ibca1d607738a4c7ed8746d09de9ca1ceaecb3415
Signed-off-by: Harry Yang <harryy@codeaurora.org>