ralink: add i2c fix

there is a deadlock that triggers under heavy bus load. until the bug is
fxed, revert to an old version of the I2C driver that does not suffer
from this issue.

Signed-off-by: John Crispin <blogic@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@49200 3c298f89-4303-0410-b956-a3cf2f4a3e73