Rework for AGL UCB integration

Rework for AGL UCB integration

Changes include:
- The provided kernel patches have been reworked to not modify the
  salvator-x(s) devicetree source, but to introduce new files for the
  reference hardware instead.  There is some possibility that the
  reference hardware devicetree could be based off the the salvator-x
  with some work and perhaps splitting of the salvator-x source, but
  for now the aim is to avoid breaking the salvator-x(s) with the
  reference hardware changes.
- The modifications to the r8a7795 pinctrl driver have been replaced
  with a splitting of the USB interface OVC pins into their own pin
  groups, which has previously been done for other older Renesas
  hardware.  This allows booting the reference hardware off of the
  same kernel as other H3 boards, at the expense of minor devicetree
  modifications for them (e.g. h3ulcb).  There is likely some more
  work required if this needs to be upstreamed, as the ulcb.dtsi
  changes would mean that the pinctrl drivers for M3 would also need
  the new pin groups.
- All changes for the ST asm330lhh driver addtion have been moved to
  that patch to the kernel.
- A machine conf file has been added for "agl-refhw-h3", and the
  firmware documentation updated to document how to set up a build of
  the firmware using it.  This is required due to the firmware options
  from this layer's arm-trusted-firmware bbappend not being compatible
  with other H3 boards (eMMC versus Hyperflash boot).  A definition
  of the COMPATIBLE_MACHINE variable has been added to that bbappend
  to make sure that attempting to use it with another H3 machine will
  trigger an error.  In AGL, the bbappend will need to be masked out
  with BBMASK for now.
- The top-level README file has been updated to reflect the expected
  integration in AGL.

Bug-AGL: SPEC-3658

Signed-off-by: Scott Murray <scott.murray@konsulko.com>