s390/boot: vmlinux.lds.S: handle commonly discarded sections

When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are several series of warnings
from the various discardable sections that the kernel adds for build
purposes that are not needed at runtime:

  s390-linux-ld: warning: orphan section `.export_symbol' from `arch/s390/boot/decompressor.o' being placed in section `.export_symbol'
  s390-linux-ld: warning: orphan section `.discard.addressable' from `arch/s390/boot/decompressor.o' being placed in section `.discard.addressable'
  s390-linux-ld: warning: orphan section `.modinfo' from `arch/s390/boot/decompressor.o' being placed in section `.modinfo'

include/asm-generic/vmlinux.lds.h has a macro for easily discarding
these sections across the kernel named COMMON_DISCARDS, use it to clear
up the warnings.
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-v1-9-8a665b3346ab@kernel.orgSigned-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/boot/vmlinux.lds.S

@@ -144,6 +144,7 @@ SECTIONS
 
 	/* Sections to be discarded */
 	/DISCARD/ : {
+		COMMON_DISCARDS
 		*(.eh_frame)
 		*(__ex_table)
 		*(*__ksymtab*)