i2c-davinci: convert clock usage after clkdev conversion

DaVinci core code has converted to the new clkdev API so
clock name strings are not needed.  Instead, just the a
'struct device' pointer is needed.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>