i2c-designware: use dynamic adapter numbering on Lynxpoint

It is not good idea to mix static and dynamic I2C adapter numbering. In
this particular case on Lynxpoint we had graphics I2C adapter which took
the first numbers preventing the designware I2C driver from using the
adapter numbers it preferred.

Since Lynxpoint support was just introduced and there is no hardware available
outside Intel we can fix this by switching to use dynamic adapter numbering
instead of static.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>