Rollup merge of #131310 - taiki-e:msp430-clobber-abi, r=Amanieu

Support clobber_abi in MSP430 inline assembly

This supports `clobber_abi` which is one of the requirements of stabilization mentioned in #93335.

Refs: Section 3.2 "Register Conventions" in [MSP430 Embedded Application Binary Interface](https://www.ti.com/lit/an/slaa534a/slaa534a.pdf)

cc ``@cr1901``

r? ``@Amanieu``

``@rustbot`` label +O-msp430

Author: tgross35