MIPS: elf_hwcap: Export userspace ASEs

A Golang developer reported MIPS hwcap isn't reflecting instructions
that the processor actually supported so programs can't apply optimized
code at runtime.

Thus we export the ASEs that can be used in userspace programs.

Reported-by: Meng Zhuo <mengzhuo1203@gmail.com>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-mips@vger.kernel.org
Cc: Paul Burton <paul.burton@mips.com>
Cc: <stable@vger.kernel.org> # 4.14+
Signed-off-by: Paul Burton <paul.burton@mips.com>