SPARC64: update localplt.data

Commits d81f90cc and 89faa034 replaced called to __isnan and __isinf
by the corresponding GCC builtins. In turns GCC emits calls to _Qp_cmp.
We should therefore add _Qp_cmp to localplt.data as otherwise the
elf/check-localplt test fails with:

   Extra PLT reference: libc.so: _Qp_cmp

A similar change has already been done for SPARC32 in commit 6ef1cb95.

Changelog:
	* sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data: Add _Qp_cmp.