lib/cbi: Move cbi.c and cbi_unittest.c to lib/cbi

BUG=b:348095503
TEST=FEATURES="test" USE="mosys_platform_arm -mosys_platform_geralt" \
     emerge-geralt mosys
TEST=FEATURES="test" emerge-geralt mosys

Change-Id: I75e71757a69f47dab552eb0995c603807e5edefb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/mosys/+/5823656
Reviewed-by: Yu-Ping Wu <[email protected]>
Reviewed-by: Jack Rosenthal <[email protected]>
Tested-by: Yidi Lin <[email protected]>
Commit-Queue: Yidi Lin <[email protected]>
8 files changed