Enable Exynos4412 TMU

Requested by ODM.

It is not clear from the TMU section of the Exynos4412 manual, but
a 1.8V supply is required on the VDD18_TS pin, as well as a 100K
resistance to ground on XtsRES_EXT, so this is something that will
have to be enabled on a board-by-board basis.
If that voltage is not supplied, the machine immediately reports
a maximum temperature of 255C and shuts down.