mm/filemap.c: remove unused argument from shrink_readahead_size_eio()

mm/filemap.c: remove unused argument from shrink_readahead_size_eio()

The first argument of shrink_readahead_size_eio() is not used.  Hence
remove it from the function definition and from all the callers.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1583868093-24342-1-git-send-email-jrdr.linux@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>