macbook21: Add CST entries

Due to the CST entries the machine uses less power running
GNU/Linux-libre. This can be seen by monitoring CPU temperature
and time left the machine can run on battery. CPU temperature
measurements have been done with lm_sensors, battery querying
with acpi. Tests have been done before applying this patch and
after. In both cases the battery was fully loaded and the machine
powered up on battery, without AC. In both tests the machine was
idleing for more than 1 hour.

Without this patch battery was predicted to last 01:52:30 hours,
CPU temperature first measurement showed 38 degrees. After 15 min
idle, temperature has reached its maximum value in this test of
61 and 62 degrees (Core 0 and 1). Fan speed begins to increase
shortly after 15 min. From its minimal value 1800 rpm it reaches
3100 rpm after 40 min. CPU temperature did not increase any further.
After 60 min idle, the battery was predicted to still last 57 min.

With this patch battery was predicted to last 02:22:40 hours. That
is plus 30 min. CPU temperature begins at 35 degrees. After 15 min
temperature has reached 45 degrees; after 30 min it has reached
the maximal temperature during this test of about 50 degrees.
That is 10 degrees improvement. The fan stayed at minimal speed.
After 60 min idle, the battery was predicted to still last 01:22:48
hours; a 25 minute improvement.

Change-Id: I6b2173df1dc09300329b61b51b79f4b9f4a8fb13
Signed-off-by: Axel Holewa <mono@posteo.de>
Reviewed-on: http://review.coreboot.org/7923
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

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