linux-user/loongarch64: Create target_ptrace.h

Remove the target_pt_regs structure from target_syscall.h.
Add target_user_pt_regs to target_ptrace.h, which matches
what is actually used on loongarch64.

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