usb: gadget: f_fs: Remove unnecessary spinlocks.

usb: gadget: f_fs: Remove unnecessary spinlocks.

Commit 24729b307eefc ("usb: gadget: f_fs: Fix race between aio_cancel()
and AIO request complete") moved the call to usb_ep_free_request() from
ffs_epfile_async_io_complete() to ffs_user_copy_worker().

In ffs_user_copy_worker(), ki_complete() is called before
usb_ep_free_request().  Once ki_complete() returns, ffs_aio_cancel() can
no longer be invoked for the completed kiocb, as ki_complete() removes it
from the &ctx->active_reqs list in aio.c.  ffs_aio_cancel() only applies
to kiocb instances still present on this list.

The potential race between ki_complete() and ffs_aio_cancel() is already
guarded by the &ctx->ctx_lock spinlock in aio.c.

As a result, there is no race condition between the usb_ep_dequeue() call
in ffs_aio_cancel() and the usb_ep_free_request() call in
ffs_user_copy_worker().  Consequently, the spin lock/unlock operations on
&io_data->ffs->eps_lock are no longer necessary.

Signed-off-by: Ingo Rohloff <ingo.rohloff@lauterbach.com>
Link: https://lore.kernel.org/r/20250701113602.33402-2-ingo.rohloff@lauterbach.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>