MIPS: SB1: Remove support for Pass 1 parts.

Pass 1 parts had a number of significant erratas and were only available
in small numbers and under NDA.  Full support also required the use of a
special toolchain that kept branches properly aligned.  These workarounds
were never upstreamed and the only toolchain known to have them is
Montavista's GCC 3.0-based toolchain which completly obsoleted if not
useless these days.

So now that automated testing has tripped over the user of the
-msb1-pass1-workarounds option, rather than fixing it remove support for
pass 1 parts.

Probably nobody will notice.  I seem to own the last know pass 1 board
and I haven't noticed another one in the wild in the past decade, at
least.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>