ARM: dts: Refactor and rename .dts files for 8974 v2.0 and v2.1

Upcoming device tree properties will require the ability to distinguish
between v2.2 hardware and older v2 variants (v2.0 and v2.1). Create
an msm8974-v2.0-1.dtsi file to specify these properties in, similar
to the msm8974-v2.2.dtsi file that already exists.

Also rename the .dts files that include msm8974-v2.0-1.dtsi to make it
clear that they are used only for v2.0 and v2.1 hardware.

Change-Id: I08cc2fd5046894dd987871900f2f933628499999
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>