Split out the I2C code to allow I2C transactions during early romstage.
TEST=Build and run on Galileo Gen2
Change-Id: I87ceb0a8cf660e4337738b3bcde9d4fdeae0159d
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: https://review.coreboot.org/15007
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
