arm64: dts: qcom: Add device tree for Samsung Galaxy A3U/A5U

Samsung Galaxy A3 (SM-A300FU) and Samsung Galaxy A5 (SM-A500FU)
are smartphones using the MSM8916 SoC released in 2015.

Add a device tree for A3U and A5U with initial support for:
  - SDHCI (internal and external storage)
  - USB Device Mode
  - UART (on USB connector via the SM5502 MUIC)
  - Regulators

The two devices (and all other variants of A3/A5 released in 2015)
are very similar, with some differences in display, touchscreen
and sensors. The common parts are shared in
msm8916-samsung-a2015-common.dtsi to reduce duplication.

The device tree is loosely based on apq8016-sbc.dtsi and the
downstream kernel provided by Samsung, mixed with a lot of own
research.

Co-developed-by: Michael Srba <Michael.Srba@seznam.cz>
Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>