To avoid userspace build failures such as:

.../linux/uio.h:37: error: expected `=', `,', `;', `asm' or `__attribute__' before `iov_length'
.../linux/uio.h:47: error: expected declaration specifiers or `...' before `size_t'

move uio functions inside a __KERNEL__ block.
Signed-off-by: NJiri Slaby <jirislaby@gmail.com>
Acked-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>