usb: chipidea: imx: improve logic if samsung,picophy-* parameter is 0

usb: chipidea: imx: improve logic if samsung,picophy-* parameter is 0

In current driver, the value of tuning parameter will not take effect
if samsung,picophy-* is assigned as 0. Because 0 is also a valid value
acccording to the description of USB_PHY_CFG1 register, this will improve
the logic to let it work.

Fixes: 58a3cefb3840 ("usb: chipidea: imx: add two samsung picophy parameters tuning implementation")
cc: <stable@vger.kernel.org>
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Acked-by: Peter Chen <peter.chen@kernel.org>
Link: https://lore.kernel.org/r/20230627112126.1882666-1-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>