IMX: don't disable the uart clock if DEBUG_LL uses it

Before the clock was left enabled only for DEBUG_LL_CONSOLE which
requires an additional patch to exist at all.  With this patch applied
DEBUG_LL_CONSOLE depends on DEBUG_LL, so this doesn't break.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>