MIPS: Delete Wind River ppmc eval board support.

This board has been EOL for many years now; lets not burden people doing
build coverage and other tree wide work with working on essentially dead
files.

[ralf@linux-mips.org: Also remove arch/mips/include/asm/mach-wrppmc/war.h.]

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Patchwork: http://patchwork.linux-mips.org/patch/5503/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>