arm64: dts: qcom: Add HP Envy x2

This adds the initial DT for the HP Envy x2 laptop.  Supported
functionality includes USB (host), microSD-card, keyboard, and trackpad.

Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>