Inconsistent .eh_frame_hdr on powerpc64

Inconsistent .eh_frame_hdr on powerpc64

There is code in bfd/elf-eh-frame.c and ld/emultempl/elf32.em that
checks for the presence of eh_frame info by testing for a section
named .eh_frame sized more than 8 bytes.   The size test is to exclude
a zero terminator.  A similar check in elf64-ppc.c wrongly just tested
for non-zero size before creating the linker generated .eh_frame
describing plt call and other linkage stubs.  The intention was to not
generate that info unless there was some user .eh_frame.  (No user
.eh_frame implies the user doesn't care about exception handling.)
Because the test in elf64-ppc.c was wrong, ld generated the stub
.eh_frame just on finding a zero .eh_frame terminator in crtend.o, but
didn't generate the corresponding .eh_frame_hdr.

	* elf64-ppc.c (ppc64_elf_size_stubs): Correct test for user
	.eh_frame info.