IOMUX: Fix stopping unused dropped consoles

IOMUX: Fix stopping unused dropped consoles

iomux_match_device() returns -ENOENT instead of the end index, which means
console_stop() is never called at the moment for unused consoles.

This prevents e.g. f_acm from releasing the USB gadget interface when
removing it from stdio/stderr/stdin.

Fixes: b672c1619bb9 ("IOMUX: Split out iomux_match_device() helper")
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>