[ARM] tegra: tegra_i2s_audio: clean up handling of state

[ARM] tegra: tegra_i2s_audio: clean up handling of state

-- Use consistently the various state flags:
   -- active is set only when there is a read or write in flight
   -- recording_canncelled is set only when recording is stopped via the ioctl()
   -- dma_has_it is used to determine whether DMA is already in flight; do not
      use the state of the fifos for this (e.g., if the TX fifo is empty, do not
      assume that playback is stopped)
   -- added a stop_completion (implemented for readers only) so that readers
      closing a stream can wait until DMA or PIO transactions are stopped
-- Split /dev/audio0_{in,out} into /dev/audio0_{in,in_ctl,out,out_ctl} where the
   _ctl versions have the ioctl()s
-- Introduced an error count per audio_stream; error count is reset on open, can
   be read back & reset through an ioctl

Signed-off-by: Iliyan Malchev <malchev@google.com>