s390/boot: vmlinux.lds.S: handle '.rela' sections

s390/boot: vmlinux.lds.S: handle '.rela' sections

When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are several warnings from
arch/s390/boot/head.o due to the unhandled presence of '.rela' sections:

  s390-linux-ld: warning: orphan section `.rela.iplt' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.head.text' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.got' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.data' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.data.rel.ro' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.iplt' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.head.text' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.got' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.data' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
  s390-linux-ld: warning: orphan section `.rela.data.rel.ro' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'

These sections are unneeded for the decompressor and they are not
emitted in the binary currently. In a manner similar to other
architectures, coalesce the sections into '.rela.dyn' and ensure it is
zero sized, which is a safe/tested approach versus full discard.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-6-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>