xfs: Remove incore use of XFS_OQUOTA_ENFD and XFS_OQUOTA_CHKD

Remove all incore use of XFS_OQUOTA_ENFD and XFS_OQUOTA_CHKD. Instead,
start using XFS_GQUOTA_.* XFS_PQUOTA_.* counterparts for GQUOTA and
PQUOTA respectively.

On-disk copy still uses XFS_OQUOTA_ENFD and XFS_OQUOTA_CHKD.

Read and write of the superblock does the conversion from *OQUOTA*
to *[PG]QUOTA*.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>