Revert: PowerPC: Don't generate unused section symbols

[Fangrui Song]

On 2021-07-24, Alan Modra via Binutils wrote:
>Blindly following x86 broke linux kernel builds.

Can the root cause in the Linux kernel be fixed instead?

ClangBuiltLinux has some PowerPC configurations with clang and its
integrated assembler (which suppresses unused STT_SECTION):
https://github.com/ClangBuiltLinux/continuous-integration2/runs/3150620586?check_suite_focus=true


If the gas change would make Linux kernel version X < threshold not
assemblable with new gas (and X is deemed important), postponing the gas
change may look fine, but it'd be better come with a notice the change
can be brought back.