docs(msm8916): document new build options

Update the MSM8916 platform documentation with the new build options
introduced in the previous changes:

  - AArch32 (BL32/SP_MIN)
  - UART selection

While at it, also document the build options that allow changing the
memory addresses (PRELOADED_BL33_BASE, BL31_BASE, BL32_BASE).

Change-Id: I2370c8264982317693f69fda0b03a255f12bafe2
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
1 file changed