Updates for BSP v5.5.0

Changes:
- Kernel patches updated for the 5.10.41 linux-renesas kernel, most
  changes are for the upstream rename of the non-engineering sample H3
  from r8a7795 to r8a77951.
- The kernel patches have been renamed to match git format-patch /
  devtool naming conventions to be a bit more consistent and hopefully
  simplify future updates.
- To maintain consistency with the other rcar3 boards, as part of the
  kernel patch updates the reference hardware devicetree has been
  renamed to r8a77951-agl-refhw, which does result in a user visible
  change in the .dtb name.
- The upstreamed, then reverted upstream patch to arm-trusted-firmware
  to disable FDT generation has been replaced with a simpler patch to
  just put "renesas,unknown" in the compatible string instead of
  panic-ing.  This should be easier to carry forward.
- Documentation updated for new branch & tag.

Bug-AGL: SPEC-4103

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I48b2cce5d55df3fff49e556821b27b8f516b98e1