LU-4276 ldiskfs: enable read/write access by default

LU-4276 ldiskfs: enable read/write access by default

Add build time config option to allow read/write access by default.
While the new CONFIG_LDISKFS_FS_RW only matters in SLES11 builds,
it's easiest to just add the flag to all builds unconditionally.
It will be ignored in builds where it doesn't matter.

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: Icaab7a4fd003dd29a49af9222852bded7ec344ff
Reviewed-on: http://review.whamcloud.com/8335
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>