usb: dwc2: gadget: Fix spin_lock/unlock mismatch in dwc2_hsotg_udc_stop()

dwc2_gadget_exit_clock_gating() internally calls call_gadget() macro,
which expects hsotg->lock to be held since it does spin_unlock/spin_lock
around the gadget driver callback invocation.

However, dwc2_hsotg_udc_stop() calls dwc2_gadget_exit_clock_gating()
without holding the lock. This leads to:
- spin_unlock on a lock that is not held (undefined behavior)
- The lock remaining held after dwc2_gadget_exit_clock_gating() returns,
causing a deadlock when spin_lock_irqsave() is called later in the
same function.

Fix this by acquiring hsotg->lock before calling
dwc2_gadget_exit_clock_gating() and releasing it afterwards, which
satisfies the locking requirement of the call_gadget() macro.

Fixes: af076a41f8a2 ("usb: dwc2: also exit clock_gating when stopping udc while suspended")
Cc: stable <stable@kernel.org>
Signed-off-by: Juno Choi <juno.choi@lge.com>
Link: https://patch.msgid.link/20260324014910.2798425-1-juno.choi@lge.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>