ASoC: dwc: Add irq parameter to DOCUMENTATION

A parameter description for the interruptions of the
I2S controller was added.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Carlos Palminha <palminha@synopsys.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org
Cc: alsa-devel@alsa-project.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>