mb/lenovo/s230u: Fix USBDEBUG check

- Change preprocessor #if to standard C if.  This will get optimized
out if the config option is disabled, but lets the compiler check the
contents.
- CONFIG_USBDEBUG is always going to be defined even if it's disabled,
so this check is not going to work as expected.
See the coreboot Kconfig documentation in /Documentation/core/Kconfig.md

Change-Id: Ia63438d9525e79307d9229ad3ffa2962978611d8
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/18974
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Tested-by: build bot (Jenkins)
1 file changed