leds: lgm-sso: Fix clock handling

The clock handling has a few issues:
 - when getting second clock fails, the first one left prepared and enabled
 - on ->remove() clocks are unprepared and disabled twice

Fix all these by converting to use bulk clock operations since both clocks
are mandatory.

Fixes: c3987cd2 ("leds: lgm: Add LED controller driver for LGM SoC")
Cc: Amireddy Mallikarjuna reddy <mallikarjunax.reddy@linux.intel.com>
Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>