include/linux/memremap.h: remove stale comments

include/linux/memremap.h: remove stale comments

Fixes: 039ca4fe8b27 ("memremap: remove the data field in struct dev_pagemap")
Fixes: ea2fa105edf4 ("memremap: remove the dev field in struct dev_pagemap")
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <dan.j.williams@intel.com>
Link: http://lkml.kernel.org/r/20200316213205.145333-1-ira.weiny@intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>