y2038: additional syscall ABI cleanup This is a follow-up to the y2038 syscall patches already merged in the tip tree. As the final 32-bit RISC-V syscall ABI is still being decided on, this is the last chance to make a few corrections to leave out interfaces based on 32-bit time_t along with the old off_t and rlimit types. The series achieves this in a few steps: - A couple of bug fixes for minor regressions I introduced in the original series - A couple of older patches from Yury Norov that I had never merged in the past, these fix up the openat/open_by_handle_at and getrlimit/setrlimit syscalls to disallow the old versions of off_t and rlimit. - Hiding the deprecated system calls behind an #ifdef in include/uapi/asm-generic/unistd.h - Change arch/riscv to drop all these ABIs. Originally, the plan was to also leave these out on C-Sky, but that now has a glibc port that uses the older interfaces, so we need to leave them in place.