OMAP3 clock: lessen amount of noisy messages

On our system we see the following messages:

Disabling unused clock "gpt2_ick"
Disabling unused clock "gpt3_ick"
Disabling unused clock "gpt4_ick"
Disabling unused clock "gpt5_ick"
...

The messages have KERN_INFO level and if you have serial
console, they normally go there. I do not think it is good
idea to print that much stuff there. Moreover, messages
are not properly prefixed and for mortals it is not
immeadietly clear where they come from.

Let's give them debugging level instead.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
[paul@pwsan.com: trimmed debugging output in patch description]