ASoC: OMAP: Fix capture pointer handling for OMAP1510 to work correctly with recent ALSA PCM code

With recent (2.6.34) chnages in PCM handling, capture stopped working on my
OMAP1510 based Amstrad Delta videophone.

Using 2.6.34-rc2, I was able to correct the problem in 3 different ways:

1. reverting commit 7b3a177b

,
2. enabling additional jiffies check with
	echo 4 >/proc/asound/card0/pcm0c0/xrun_debug
3. applying the patch below.

Since I wasn't able to reproduce the problem on my i686 PC, I guess the
problem is probably machine specific.

The patch reuses the method for software emulation of missing hardware
pointer, already implemented for playback on OMAP1510. It's possible that
event if a hardware pointer is available for capture on this machine, its
behaviour may be not compatible with what upper layer expects.

If you think the problem may be more general and should be solved differently,
on a higher level, I can try to work more on it if you give me a hint.

If the patch gets accepted, I suggest it goes as a fix in the current release
cycle.

Created and tested against linux-2.6.34-rc2.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>