APX: Add R_X86_64_CODE_4_GOTPC32_TLSDESC
For TLS instruction:
lea foo@tlsdesc(%rip), %reg
add
#define R_X86_64_CODE_4_GOTPC32_TLSDESC 45
if the instruction starts at 4 bytes before the relocation offset. This should be used if reg is one of the additional general-purpose registers, r16-r31, in Intel APX. It is similar to R_X86_64_GOTPC32_TLSDESC and linker optimization must take the different instruction encoding into account.