serial: imx: change SERIAL_IMX_CONSOLE to bool

serial: imx: change SERIAL_IMX_CONSOLE to bool

SERIAL_IMX_CONSOLE is a build option for the imx driver (SERIAL_IMX).
It does not build a separate console driver file, so it can't be built
as a module since it isn't built at all.

Change the Kconfig symbol from tristate to bool and update the help
text accordingly.

Fixes: 0db4f9b91c86 ("tty: serial: imx: enable imx serial console port as module")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20260110232643.3533351-2-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>