[SPARC64]: Fix several bugs in flush_ptrace_access().

1) Use cpudata cache line sizes, not magic constants.
2) Align start address in cheetah case so we do not get
   unaligned address traps.  (pgrep was good at triggering
   this, via /proc/${pid}/cmdline accesses)

Signed-off-by: David S. Miller <davem@davemloft.net>