usb: phy: generic: Use proper helper for property detection

usb: phy: generic: Use proper helper for property detection

Since commit c141ecc3cecd7 ("of: Warn when of_property_read_bool() is
used on non-boolean properties") a warning is raised if this function
is used for property detection. of_property_present() is the correct
helper for this.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Link: https://lore.kernel.org/r/20250120144251.580981-1-alexander.stein@ew.tq-group.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>