metag/usercopy: Add early abort to copy_to_user

metag/usercopy: Add early abort to copy_to_user

commit fb8ea062a8f2e85256e13f55696c5c5f0dfdcc8b upstream.

When copying to userland on Meta, if any faults are encountered
immediately abort the copy instead of continuing on and repeatedly
faulting, and worse potentially copying further bytes successfully to
subsequent valid pages.

Fixes: 373cd784d0fc ("metag: Memory handling")
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>