hfsplus: quieten down mounting hfsplus journaled fs read only

Check whether the file system was to be mounted read only anyway before
warning about changing the mount to read only.

Signed-off-by: Mike Crowe <mac@mcrowe.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>