[binutils-gdb] Correct elf64-ppc.c linkage stub comment and formatting fixes

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 2cdcc33021214e77c2c185aa78ad4f9ae1b9e565 ***

Author: Alan Modra <amodra@gmail.com>
Branch: master
Commit: 2cdcc33021214e77c2c185aa78ad4f9ae1b9e565

Correct elf64-ppc.c linkage stub comment and formatting fixes

ppc_stub_long_branch_notoc will never need more than a 32-bit offset
for the r12 offset since the stub target must be in range of a
branch instruction.

	* elf64-ppc.c: Correct ppc_stub_long_branch_notoc example.
	Formatting.