RISC-V: Use 64-bit time_t and off_t for RV32 and RV64

RISC-V: Use 64-bit time_t and off_t for RV32 and RV64

Using the original glibc headers under bits/ let's make small
modifications to use 64-bit time_t and off_t for both RV32 and RV64.

For the typesizes.h, here are justifications for the changes from the
generic version (based on Arnd's very helpful feedback):
- All the !__USE_FILE_OFFSET64 types (__off_t, __ino_t, __rlim_t, ...)
  are changed to match the 64-bit replacements.

- __time_t is defined to 64 bit, but no __time64_t is added. This makes
  sense as we don't have the time64 support for other 32-bit
  architectures yet, and it will be easy to change when that happens.

- __suseconds_t is 64-bit. This matches what we use the kernel ABI for
  the few drivers that are relying on 'struct timeval' input arguments
  in ioctl, as well as the adjtimex system call. It means that timeval
  has to be defined without the padding, unlike timespec, which needs
  padding.

Reviewed-by: Maciej W. Rozycki <macro@wdc.com>