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.

Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>