Fix voltage sense values for kda boards.
Add support for newer all-NFET Multistar 30A boards (kda_nfet).
Make tp_8khz include tp rather than duplicating the settings.
Add 8khz target for early 2014 Multistar 30A boards that have problems.
Remove calibrated support for Maytech 20A, 30A, 40A, 60A.

Maytech reports this seems to cause problems with their boards now.

This reverts commit 7ec97b3ad1ec7c92cbd75f8780d880fa5bea4f50.
Really add support for newer all-NFET Multistar 30A boards (kda_nfet).
Merged from SimonK's repo.