ASoC: codecs: fix edid error when hdmi ops is null

When edid mixer control is executed, if the hdmi ops is
not set, the mixer control get_info() returns error.
This error is treated as fatal by the caller.

Fix by returning valid mixer control info when hdmi ops
is null.

Change-Id: I0097a75d94690b199fab1adc7f2ff3faa2d82e7b
Signed-off-by: Shiv Maliyappanahalli <smaliyap@codeaurora.org>