ARM: OMAP4 clock domain: Add check for avoiding dependency related update.

A check is added for avoiding the sleep/wakeup dependency updates
for OMAP4 as the structures for the dependencies are currently absent.

Signed-off-by: Abhijit Pagare <abhijitpagare@ti.com>
[paul@pwsan.com: added warnings, explanatory comment, copyright update]
Signed-off-by: Paul Walmsley <paul@pwsan.com>