cramfs: convert to use vmf_insert_mixed

cramfs: convert to use vmf_insert_mixed

cramfs is the only remaining user of vm_insert_mixed() and should be
converted to vmf_insert_mixed().

Based on a previous patch from Matthew Wilcox.

Link: http://lkml.kernel.org/r/nycvar.YSQ.7.76.1808290945450.10215@knanqh.ubzr
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>a
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>