usb: dwc3: of-simple: fix missing clk_disable_unprepare

If of_clk_get() fails, the clean-up of already initialized clocks should be
the same as when clk_prepare_enable() fails. Thus a clk_disable_unprepare()
for each clock should be called before the clk_put().

Found by Linux Driver Verification project (linuxtesting.org).

Fixes: 16adc674 ("usb: dwc3: ep0: fix setup_packet_pending initialization")

Signed-off-by: Andreas Platschek <andreas.platschek@opentech.at>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>