ARM: OMAP2+: devices: Do not print error when dss_hdmi hwmod lookup fails

The dss_hdmi hwmod is used to create the HDMI audio device for OMAP4+
When we boot the kernel we can silently ignore the failure since the IP
does not exist on them.

Reported-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>