[ALSA] Support multiple capture rates on p16v.

EMU10K1/EMU10K2 driver
The capture rate does in fact vary, but it only captures anything if
the HD Capture source is set to I2S or AC97. I have not tested if the sound
is actually captured from an physical input of some type or not.
TODO: Get SPDIF capture working.

Signed-off-by: James Courtier-Dutton <James@superbug.co.uk>