ARM: dts: msm: remove extraneous properties from LDO 28 device on SDM845

Remove the extraneous mboxes and qcom,resource-name properties
from within the regulator-l28 node since they have no effect
in second level rpmh-regulator device nodes.

Change-Id: I4a4b4275ac878c108e8580689f52f68f27d9da6c
Signed-off-by: David Collins <collinsd@codeaurora.org>