ASoC: omap-pcm: off-by-one in 'omap_pcm_limit_supported_formats'

When calling 'snd_pcm_format_physical_width', SNDRV_PCM_FORMAT_LAST is a
valid value, so don't skip it.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>