[Skiboot] skiboot-5.4.2 released

[Stewart Smith]

Release notes below:

skiboot-5.4.2 was released on Friday December 2nd 2016. It replaces
skiboot-5.4.1 as the current stable release.

Over skiboot-5.4.1, we have two bug fixes exclusively aimed at machines
with TPMs:

- i2c: Add nuvoton TPM quirk, disallowing i2cdetect as it can hard lock the TPM
- p8-i2c improve I2C reset code path, solves getting stuck resetting i2c engine

-- 
Stewart Smith
OPAL Architect, IBM.