wil6210: allocate rx reorder buffer only if rx reorder is enabled

wil_addba_rx_request allocates the rx reorder buffer regardless
of use_rx_hw_reordering settings.
Fix this by checking wil->use_rx_hw_reordering before allocating
the reorder buffer.

Change-Id: Ide0d2ad0b3851789f653b7fa1c6c9a66c08cf270
Signed-off-by: Maya Erez <merez@codeaurora.org>