Fix printing of invalid struct xfs_dqblk.d_flags

* quota.c (decode_cmd_data): Explicitly cast struct xfs_dqblk.d_flags
to uint8_t to avoid potential sign-extension bug when printing
invalid struct xfs_dqblk.d_flags.
diff --git a/quota.c b/quota.c
index c73ac6d..0a388b2 100644
--- a/quota.c
+++ b/quota.c
@@ -317,7 +317,7 @@
 			tprintf("{version=%d, ", dq.d_version);
 			tprints("flags=");
 			printflags(xfs_dqblk_flags,
-				   dq.d_flags, "XFS_???_QUOTA");
+				   (uint8_t) dq.d_flags, "XFS_???_QUOTA");
 			tprintf(", fieldmask=%#x, ", dq.d_fieldmask);
 			tprintf("id=%u, ", dq.d_id);
 			tprintf("blk_hardlimit=%" PRIu64 ", ", dq.d_blk_hardlimit);