powerpc64-ld infinite loop

If this code dealing with possible conversion of inline plt sequences
is ever executed, ld will hang.  A binary with such sequences and of
code size larger than approximately 90% the reach of an unconditional
branch is the trigger.  Oops.

	* elf64-ppc.c (ppc64_elf_inline_plt): Do increment rel in for loop.

(cherry picked from commit 435edf0bf231240ccecb474b74ebb49dc8db2633)