Update nios2 localplt.data.

This patch updates nios2 localplt.data so the localplt test passes in
my compile-only all-ABIs glibc testing.  A new PLT entry for
__extendsfdf2 is added.

Tested for nios2.

	* sysdeps/unix/sysv/linux/nios2/localplt.data: Add __extendsfdf2
	for libc.so.