wifi: mwifiex: fix uninitialized firmware_stat

wifi: mwifiex: fix uninitialized firmware_stat

Variable firmware_stat is possible to be used without initialization.

Signed-off-by: David Lin <yu-hao.lin@nxp.com>
Fixes: 1c5d463c0770 ("wifi: mwifiex: add extra delay for firmware ready")
Cc: stable@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202312192236.ZflaWYCw-lkp@intel.com/
Acked-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231221015511.1032128-1-yu-hao.lin@nxp.com