[POWERPC] ptrace shouldn't touch FP exec mode

[POWERPC] ptrace shouldn't touch FP exec mode

One of the gratuitous difference between 32 and 64-bit ptrace is
whether you can whack the MSR:FE0 and FE1 bits from ptrace.  This
patch forbids it unconditionally.  In addition, the 64-bit kernels
used to return the exception mode in the MSR on reads, but 32-bit
kernels didn't.  This patch makes it return those bits on both.

Finally, since ptrace-ppc32.h and ptrace-ppc64.h are mostly empty now, and
since the previous patch made ptrace32.c no longer need the MSR_DEBUGCHANGE
definition, we just remove those 2 files and move back the remaining bits
to ptrace.c (they were short lived heh ?).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>