ASoC: i.MX SSI: Fix DSP_A format.

commit 5ed80a75b248bfaf840ea6b38f941edcf6ee7dc7 upstream.

According to i.MX27 Reference Manual (p 1593) TXBIT0 bit selects
whether the most significant or the less significant part of the
data word written to the FIFO is transmitted.

As DSP_A is the same as DSP_B with a data offset of 1 bit, it
doesn't make any sense to remove TXBIT0 bit here.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>