qcacmn: Ensure rx_desc->unmapped is set to 1 before releasing lock

Originally Change-Id: I9fa71bdb6d4e4aa93fc795cc5dd472a181325991
was brought in to fix a race condition between Rx buffers
map/unmapped in dp_ipa_handle_rx_buf_smmu_mapping() and at the
same time map/unmapped from dp rx replenish context.
The fix ensured that rx_desc is unmapped and rx_desc->unmapped=1
flag will be set atomically within a lock.

But Change-Id: Iadb40071fb733cc4de3291784df5075d5a099a8e
introduced a flaw by releasing the lock before setting the flag to 1.

This is currently causing race condition and causing double
unmap calls when IPA smmu pool unmap and dp_rx_replenish unmap
is running in parallel. This change will fix this issue, by setting
the flag before the lock is released.

Change-Id: I3533bb5f6cc0437395149cd3c718826ef0b482a3
CRs-Fixed: 3594252

dp/wifi3.0/dp_rx.h

@@ -2769,6 +2769,7 @@ void dp_rx_nbuf_unmap(struct dp_soc *soc,
 	qdf_nbuf_unmap_nbytes_single(soc->osdev, rx_desc->nbuf,
 				     QDF_DMA_FROM_DEVICE,
 				     rx_desc_pool->buf_size);
+	rx_desc->unmapped = 1;
 
 	dp_ipa_reo_ctx_buf_mapping_unlock(soc, reo_ring_num);
 }