UAPI: Unexport linux/blk_types.h

It seems that was linux/blk_types.h incorrectly exported to fix up some missing
bits required by the exported parts of linux/fs.h (READ, WRITE, READA, etc.).

So unexport linux/blk_types.h and unexport the relevant bits of linux/fs.h.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jens Axboe <jaxboe@fusionio.com>
cc: Tejun Heo <tj@kernel.org>
cc: Al Viro <viro@ZenIV.linux.org.uk>