staging: wfx: fix an error handling in wfx_init_common()
In the Linux kernel, the following vulnerability has been resolved:

staging: wfx: fix an error handling in wfx_init_common()

One error handler of wfx_init_common() return without calling
ieee80211_free_hw(hw), which may result in memory leak. And I add
one err label to unify the error handler, which is useful for the
subsequent changes.