serial: sccnxp: Fix error handling in sccnxp_probe()

commit c91261437985d481c472639d4397931d77f5d4e9 upstream.

sccnxp_probe() returns result of regulator_disable() that may lead
to returning zero, while device is not properly initialized.
Also the driver enables clocks, but it does not disable it.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>