Revert "HACK: i2c: designware: Slow down all buses for now"

This reverts commit 0e09f781d3b087dacd273b174c0cf717a9dc9774.

Not needed. Fix was done in BIOS by changing I2C timings.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>