avr32: switch to RAW_COPY_USER

This one needs profiling; use of asm variant of access_ok() might have
been performance-critical.  Now copy_{to,from}_user() are using the
C variant.  I doubt that it's going to have visible effects, but
that needs to be experimentally verified.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>