m32r: use generic sys_pipe

m32r can use the generic sys_pipe implementation.

The current sys_pipe implementation on m32r only differes from the
generic one by passing a lot of additional unused registers to sys_pipe.

Reviewed and tested by Hirokazu Takata.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>