Remove a spurious reference to ProcessElfCore

We were referencing a the process class from a register context, which seems
intuitively wrong. Also, the comment above that code is now definitely incorrect,
as ProcessElfCore now does support floating point registers. Also, the code
wasn't really doing anything, as it was just skipping a zero-initialization of a
field that was most likely zero-initialized anyway. Linux elf core FPR test still
passes after this.

llvm-svn: 288237