riscv: s64ilp32: Add TImode (128 int) support

The s64ilp32 uses 64bit compiler, so it could support “Tetra
Integer” mode, which represents a sixteen-byte (128) integer.

It's the first 32BIT linux support TImode :)

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>