In kabylake_set_bias_level(), enabling mclk may fail if the clock has
already been enabled by the firmware. Attempts to disable that clock
later will fail with a warning backtrace.

mclk already disabled
WARNING: CPU: 2 PID: 108 at drivers/clk/clk.c:952 clk_core_disable+0x1b6/0x1cf
...
Call Trace:
 clk_disable+0x2d/0x3a
 kabylake_set_bias_level+0x72/0xfd [snd_soc_kbl_rt5663_rt5514_max98927]
 snd_soc_card_set_bias_level+0x2b/0x6f
 snd_soc_dapm_set_bias_level+0xe1/0x209
 dapm_pre_sequence_async+0x63/0x96
 async_run_entry_fn+0x3d/0xd1
 process_one_work+0x2a9/0x526
...

Only disable the clock if it has been enabled.

Fixes: 15747a80 ("ASoC: eve: implement set_bias_level function for rt5514")
Cc: Brent Lu <brent.lu@intel.com>
Cc: Curtis Malainey <cujomalainey@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20201111205434.207610-1-linux@roeck-us.netSigned-off-by: Mark Brown <broonie@kernel.org>