arm64: dts: qcom: msm8992-lg-bullhead: Place LG Bullhead generic code into a DTSI file

This patch puts the generic code common across all hardware revisions
into a DTSI file.

It also prefixes the DTS filename with the vendor name, to follow the
naming convention used by other DTS files.

Signed-off-by: Jean THOMAS <virgule@jeanthomas.me>
Reviewed-by: Petr Vorel <petr.vorel@gmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211201231832.188634-1-virgule@jeanthomas.me