s390: vmlinux.lds.S: explicitly keep various sections

When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are some warnings around certain
ELF sections:

  s390-linux-ld: warning: orphan section `.dynstr' from `arch/s390/kernel/head64.o' being placed in section `.dynstr'
  s390-linux-ld: warning: orphan section `.dynamic' from `arch/s390/kernel/head64.o' being placed in section `.dynamic'
  s390-linux-ld: warning: orphan section `.hash' from `arch/s390/kernel/head64.o' being placed in section `.hash'
  s390-linux-ld: warning: orphan section `.gnu.hash' from `arch/s390/kernel/head64.o' being placed in section `.gnu.hash'

Explicitly keep those sections like other architectures when
CONFIG_RELOCATABLE is enabled, which is always true for s390.

[hca@linux.ibm.com: keep sections instead of discarding]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-4-8a665b3346ab@kernel.orgSigned-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/vmlinux.lds.S

@@ -200,6 +200,18 @@ SECTIONS
 		*(.rela*)
 		__rela_dyn_end = .;
 	}
+	.dynamic ALIGN(8) : {
+		*(.dynamic)
+	}
+	.dynstr ALIGN(8) : {
+		*(.dynstr)
+	}
+	.hash ALIGN(8) : {
+		*(.hash)
+	}
+	.gnu.hash ALIGN(8) : {
+		*(.gnu.hash)
+	}
 
 	. = ALIGN(PAGE_SIZE);
 	__init_end = .;		/* freed after init ends here */