ARM: qcom: Add ARCH_MSM8916 for MSM8916 on ARM32

Add a CONFIG_ARCH_MSM8916 option to enable building MSM8916 support
on ARM32. Note that since ARM64 is the main supported architecture
for MSM8916 this is only intended for testing and for devices where
signed firmware does not allow booting ARM64 kernels.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211004204955.21077-7-stephan@gerhold.net