tmimsp: clean up open drain for sht1x DATA

tmimsp: clean up open drain for sht1x DATA

Rename Msp430OpenDrainC to Msp430ODPUC and fix it up.  This is an
open-drain component that also provides an internal pull-up so an
external one is not required.  It only works on MSP430 pins offering
internal pull up/down feature.

The OpenDrainC component provides an open-drain emulation, does not
provide an internal pull-up, and should work for any microcontroller
having a GeneralIO implementation for its GPIO pins.