sparc: boot mmu support

Get enough of the mmu working to be able to allocate memory.

Unlike on PowerPC, we get both address and size as 64bit values. So
adjust of_region to allow this.

Also unlike the PPC port, we do not drive the hardware directly, instead we
rely on the openboot primitives to manage the translation table. This
allows staying independant of the hardware, which is a good idea at
least for the bootloader (we can do actual hardware things in the
kernel)

Change-Id: Ifa57619d3a09b8f707e1f8640d8b4f71bb717e2a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1482
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

sparc: fix bootloader build

- Add various missing jamfiles
- Add required implementation stubs
- Update openfirmware jamfiles for multiboot support
- Update linker rules for sparc loader

Change-Id: I2d06c7a4d33827f58d82946687003f9a0dcb1b7d
Reviewed-on: https://review.haiku-os.org/c/1329
Reviewed-by: waddlesplash <waddlesplash@gmail.com>