ARM: dts: apq: enable dsi device node for dragonboard8074

Enable dsi panel device nodes by default so
they are available for the respective controllers
to initialize when required. This allows to implement
the ability to override the choice of default primary
display panel which can be used for panel characterization
purposes.

Change-Id: I32bbf28f77761ca9d62cf3e3ce31f99033e1fb3c
Signed-off-by: Asaf Penso <apenso@codeaurora.org>