staging: r8188eu: remove _rtw_mutex_{init,free}

staging: r8188eu: remove _rtw_mutex_{init,free}

While testing Fabio's patch I hit lockdep warning about possible
deadlock:

[  252.063305] WARNING: possible recursive locking detected
[  252.063642] 5.14.0+ #9 Tainted: G         C
[  252.063946] --------------------------------------------
[  252.064282] ip/335 is trying to acquire lock:
[  252.064560] ffff888009ebad28 (pmutex){+.+.}-{4:4}, at: usbctrl_vendorreq+0xc5/0x4a0 [r8188eu]
[  252.065168]
[  252.065168] but task is already holding lock:
[  252.065536] ffffffffc021b3b8 (pmutex){+.+.}-{4:4}, at:  netdev_open+0x3a/0x5f [r8188eu]
[  252.066085]
[  252.066085] other info that might help us debug this:
[  252.066494]  Possible unsafe locking scenario:
[  252.066494]
[  252.066866]        CPU0
[  252.067025]        ----
[  252.067184]   lock(pmutex);
[  252.067367]   lock(pmutex);

There is one problem with this warning: there is no pmutex in this
driver, *BUT* all mutexes are initialized via private _rtw_mutex_init
API, which had struct mutex *pmutex argument.

So, all mutexes in this driver had same name in lockdep map. Of course,
lockdep will complain about any nested locking.

Fix it by open-coding _rtw_mutex_{init,free} wrappers, because we do not
need them at all.

Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20210904124747.30050-1-paskripkin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>