lld/ELF: Parse MSP430 BFD/emulation names

Follow the naming set by TI's own GCC-based toolchain.
Also, force the `osabi` field to `ELFOSABI_STANDALONE`, this matches GNU LD's output (the patching is done in `elf32_msp430_post_process_headers`).

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D92931