linux-user/mips: Use target_ulong for target_elf_greg_t

Make use of the fact that target_elf_gregset_t is a proper structure.
The target_ulong type matches the abi_ulong/abi_ullong
selection within mips64/target_elf.h.

Drop ELF_NREG, target_elf_greg_t, and tswapreg.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
3 files changed