86xx: Rearrange the sequence in start.S

86xx: Rearrange the sequence in start.S

* split the BAT initialization so that only 2 BATs (for the boot page
and stack) are programmed very early on.  The rest are initialized later.
* Move other BAT setup,  ccsrbar setup, and law setup later in the code
after translation has been enabled.

These changes will facilitate the moving of law and BAT initialization
to C code, and will aid with 36-bit physical addressing support.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>