ALSA: emu10k1: query rate of external clock sources on E-MU cards

ALSA: emu10k1: query rate of external clock sources on E-MU cards

The value isn't used yet; the subsequent commits will do that.

This ignores the existence of rates above 48 kHz, which is fine, as the
hardware will just switch to the fallback clock source when fed with a
rate which is incompatible with the base clock multiplier, which
currently is always x1.

The sample rate display in /proc spdif-in is adjusted to reflect our
understanding of the input rates.

This is tested only with an 0404b card without sync card, so there is a
lot of room for improvement.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230612191325.1315854-4-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>