mm/gup: rename nr as nr_pinned in get_user_pages_fast()

mm/gup: rename nr as nr_pinned in get_user_pages_fast()

To better reflect the held state of pages and make code self-explaining,
rename nr as nr_pinned.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Link: http://lkml.kernel.org/r/1584876733-17405-2-git-send-email-kernelfans@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>