usb: dwc3: core: Fix timeout check

usb: dwc3: core: Fix timeout check

dwc3_core_init loops 'timeout' times to check if the IP block is out
of reset using 'while (timeout--)'. If there is some issue and
the block doesn't come out of reset, the loop will run till
'timeout' becomes zero and the post decrement operator would set
timeout to 0xffffffff. Though the IP block is not out reset, the
subsequent if check 'if !timeout' would fail as timeout is not
equal to zero and the function proceeds with the initialization.

Use poll API instead to resolve this.

Signed-off-by: Varadarajan Narayanan <quic_varada@quicinc.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>