Implement R_AARCH64_TLS_DTPMOD64 and A_AARCH64_TLS_DTPREL64 relocations.

Implement R_AARCH64_TLS_DTPMOD64 and A_AARCH64_TLS_DTPREL64 relocations.
Although these are slightly obsolete in favor of R_AARCH64_TLSDESC,
gcc -mtls-dialect=trad still use them.

Please note that definition of TLS_DTPMOD64 and TLS_DTPREL64 are incorrectly
exchanged in GNU binutils. TLS_DTPREL64 should be encoded to 1028 (as is
defined in ARM ELF ABI) but binutils encode it to 1029. And vice versa,
TLS_DTPMOD64 should be encoded to 1029 but binutils encode it to 1028.

While I'm in, add also R_AARCH64_NONE. It can be produced as result of linker
relaxation.

MFC after:	1 week