ARM: dts: msm: refactor DT files for 8996 automotive platforms

Currently, all the SOC (msm8996v3AU or msm8996proAU) specific
overrides are being done in board files. There is a lot of duplication
because of that. Refactor the device tree files for 8996 automotive
platforms so that all the SOC specific overrides can be present in
msm8996v3-auto.dtsi and msm8996pro-auto.dtsi alone. All the
8996v3/8996pro automotive board files will include one of these
files based upon the SOC used.

CRs-Fixed: 1036992
Change-Id: I2306907bbda6c2604bace046b361d1895f324361
Signed-off-by: Atul Raut <araut@codeaurora.org>
Signed-off-by: Tholkappiyan Agaram Raghupathy <traghu@codeaurora.org>
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>