OMAPDSS: hdmi5: Change hdmi_wp idlemode to to no_idle for audio playback

Enabling idle mode during audio playback causes the glitches on OMAP5
HDMI. The TRM also suggests to use no-idle for HDMI audio playback.

This patch sets HDMI idle mode to no-idle for the duration of the
playback, and restores it back to original value afterwards.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>