Refactor and document the Freescale PIXIS code, used on most 85xx and 86xx
boards.  This makes the code easier to read and more flexible.

Delete pixis.h, because none of the exported functions were actually being
used by any other file.  Make all of the functions in pixis.c 'static'.
Remove "#include pixis.h" from every file that has it.

Remove some unnecessary #includes.

Make 'pixis_base' into a macro, so that we don't need to define it in every
function.

Add "while(1);" loops at the end of functions that reset the board, so that
execution doesn't continue while the reset is in progress.

Replace in_8/out_8 calls with clrbits_8, setbits_8, or clrsetbits_8, where
appropriate.

Replace ulong/uint with their spelled-out equivalents.  Remove unnecessary
typecasts, changing the types of some variables if necessary.

Add CONFIG_SYS_PIXIS_VCFGEN0_ENABLE and CONFIG_SYS_PIXIS_VBOOT_ENABLE to make
it easier for specific boards to support variations in the PIXIS registers
sets.  No current boards appears to need this feature.

Fix the definition of CONFIG_SYS_PIXIS_VBOOT_MASK for the MPC8610 HPCD.
Apparently, "pixis_reset altbank" has never worked on this board.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>