ASoC: davinci: fix sample rotation

McASP serial audio engine needs different rotation values on TX and RX
channels. Commit dde109fb462 ("ASoC: McASP: Fix data rotation for
playback. Enables 24bit audio playback") changed the calculation to fix
the playback format, but broke the capture stream by doing it for both
TXFMT and RXFMT.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Michal Bachraty <michal.bachraty@streamunlimited.com>
Cc: stable@vger.kernel.org [3.9 only]