Support for CS5343 and CS5344  24 bit ADC connected to Raspberry Pi

Changes proposed in this pull request provide support for CS5343/CS5344 24 bit analog to digital converters.
Driver assumes, that the ADC works with MCLK connected to independent 18,432 MHz clock,
and works in Master Single Speed Mode, with clock ratio: 192x/384x/768x MCLK/LRCK
(see http://www.cirrus.com/en/pubs/proDatasheet/CS5343_F3.pdf page 14 for details).
So SDOUT must be pulled up to VCC to select the Master Mode,
LRCK must be left without external pullup or pulldown resistor to select Single Speed Mode, and SCLK must be pulled up to select clock ratio: 192x/384x/768x MCLK/LRCK.

Of course pins are connected as follows:
CS534x        Raspberry Pi
SCLK            PCM_CLK (P5-03)
LRCK            PCM_FS   (P5-04)
SDOUT         PCM_DIN (P5-05)

Described setup handles only 2 channel recording with 48000Hz sampling frequency.
I have successfully recorded sound with:
arecord -D hw:1,1 -f S32_LE -c 2 -r 48000 /tmp/test1.wav  (for CS5344)
and
arecord -D hw:1,0 -f S32_LE -c 2 -r 48000 /tmp/test2.wav (for CS5343)