btrfs: tracepoints: Fix bad entry members of qgroup events

[BUG]
For btrfs:qgroup_meta_reserve event, the trace event can output garbage:

  qgroup_meta_reserve: 9c7f6acc-b342-4037-bc47-7f6e4d2232d7: refroot=5(FS_TREE) type=DATA diff=2
  qgroup_meta_reserve: 9c7f6acc-b342-4037-bc47-7f6e4d2232d7: refroot=5(FS_TREE) type=0x258792 diff=2

The @type can be completely garbage, as DATA type is not possible for
trace_qgroup_meta_reserve() trace event.

[CAUSE]
Ther are several problems related to qgroup trace events:
- Unassigned entry member
  Member entry::type of trace_qgroup_update_reserve() and
  trace_qgourp_meta_reserve() is not assigned

- Redundant entry member
  Member entry::type is completely useless in
  trace_qgroup_meta_convert()

Fixes: 4ee0d883 ("btrfs: qgroup: Update trace events for metadata reservation")
CC: stable@vger.kernel.org # 4.10+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>