drivers: serial: opentitan: remove bogus depends on clause

CONFIG_SERIAL_SUPPORT_INTERRUPT is a Kconfig option that is supposed to
be selected by serial drivers that support interrupts. This commit
removes a bogus "depends on !SERIAL_SUPPORT_INTERRUPT" which does not
make sense and causes some tests to fail.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

drivers/serial/Kconfig.opentitan

@@ -5,7 +5,6 @@ config UART_OPENTITAN
 	bool "OpenTitan UART"
 	default y
 	depends on DT_HAS_LOWRISC_OPENTITAN_UART_ENABLED
-	depends on !SERIAL_SUPPORT_INTERRUPT
 	select SERIAL_HAS_DRIVER
 	help
 	  Enable OpenTitan UART serial driver