serial: liteuart: relax compile-test dependencies

The LITEX symbol is neither a build or runtime dependency for the
liteuart serial driver.

LITEX is selected by the "LiteX SoC Controller" driver, which does a
probe-time register-access sanity check and panics if the SoC has not
been configured correctly. That driver's Kconfig entry asserts that any
LiteX driver using the LiteX register accessors should depend on LITEX,
but currently only the serial driver complies.

Relax this LITEX "dependency" in order to make it easier to compile test
the driver.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211117100512.5058-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1533,7 +1533,7 @@ config SERIAL_LITEUART
 	tristate "LiteUART serial port support"
 	depends on HAS_IOMEM
 	depends on OF || COMPILE_TEST
-	depends on LITEX
+	depends on LITEX || COMPILE_TEST
 	select SERIAL_CORE
 	help
 	  This driver is for the FPGA-based LiteUART serial controller from LiteX