ALSA: hda: clarify comments on SCF changes

ALSA: hda: clarify comments on SCF changes

The commit 1f9d3d98694b1 ("ALSA: hda - set intel audio clock to a
proper value") added a number of misleading comments.

There is no ability to detect if an SCF value was set or not, what the
code does is prevent the use of the 6MHz audio clock represented by
the value 0 in LCTL.SCF. Changing the SCF settings does require the
link to be power-cycled, but in all other cases the link is powered
automatically when exiting reset. In other words, the power-cycle is
an exception to the rule that the HDaudio legacy driver does not need
to program SPA/CPA bits.

In addition, the SCF related changes are only relevant for the first
link.

No functionality change, only comment clarifications.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Link: https://lore.kernel.org/r/20221031195505.249929-1-pierre-louis.bossart@linux.intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>