s390/boot/vmlinux.lds.S: Ensure bzImage ends with SecureBoot trailer

s390/boot/vmlinux.lds.S: Ensure bzImage ends with SecureBoot trailer

Since commit 3e86e4d74c04 ("kbuild: keep .modinfo section in
vmlinux.unstripped") the .modinfo section which has SHF_ALLOC ends up
in bzImage after the SecureBoot trailer. This breaks SecureBoot because
the bootloader can no longer find the SecureBoot trailer with kernel's
signature at the expected location in bzImage. To fix the bug,
move discarded sections before the ELF_DETAILS macro and discard
the .modinfo section which is not needed by the decompressor.

Fixes: 3e86e4d74c04 ("kbuild: keep .modinfo section in vmlinux.unstripped")
Cc: stable@vger.kernel.org
Suggested-by: Vasily Gorbik <gor@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>