Fix improper handling of R_SPARC_GOTDATA_OP_LOX10 relocation.

The fall-through in Target_sparc::Relocate::relocate for
R_SPARC_GOTDATA_OP_LOX10 is currently R_SPARC_GOT13, but should
clearly be R_SPARC_GOT10. GCC has been seen to emit a sethi/xor
rather than a sethi/or sequence to load a 32-bit immediate, but
if R_SPARC_GOT13 is used then bits 10-12 get zeroed out as both
the sethi and xor immediates contain them.

gold/
	PR gold/20442
	* sparc.cc (Target_sparc::Relocate::relocate): R_SPARC_GOTDATA_OP_LOX10
	should fall back on R_SPARC_GOT10, not R_SPARC_GOT13.