Merge changes I0d17ba6c,I540741d2,I9e6475ad,Ifd769320,I12c04a85, ... into integration

* changes:
  plat/mediatek/mt81*: Use new bl31_params_parse() helper
  plat/rockchip: Use new bl31_params_parse_helper()
  Add helper to parse BL31 parameters (both versions)
  Factor out cross-BL API into export headers suitable for 3rd party code
  Use explicit-width data types in AAPCS parameter structs
  plat/rockchip: Switch to use new common BL aux parameter library
  Introduce lightweight BL platform parameter library