[PATCH AUTOSEL 5.1 001/219] ath10k: Check tx_stats before use it

From: Yingying Tang [ Upstream commit 9e7251fa38978b85108c44743e1436d48e8d0d76 ] tx_stats will be freed and set to NULL before debugfs_sta node is removed in station disconnetion process. So if read the debugfs_sta node there may be NULL pointer error. Add check for tx_stats before use it to

[PATCH AUTOSEL 5.1 001/219] ath10k: Check tx_stats before use it

From: Yingying Tang [ Upstream commit 9e7251fa38978b85108c44743e1436d48e8d0d76 ] tx_stats will be freed and set to NULL before debugfs_sta node is removed in station disconnetion process. So if read the debugfs_sta node there may be NULL pointer error. Add check for tx_stats before use it to