[S390] reipl: move dump_prefix_page out of text section.

Reipl doesn't work on older machines were s390_reset_machine() gets
called. The reason is that the text section is read-only but the
variable dump_prefix_page is there. Since s390_reset_machine() writes
to it we get a protection exception.
Therefore move dump_prefix_page to the bss section.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/include/asm-s390/ipl.h b/include/asm-s390/ipl.h
index 5650d3d..660f782 100644
--- a/include/asm-s390/ipl.h
+++ b/include/asm-s390/ipl.h
@@ -74,6 +74,7 @@
 extern u32 ipl_flags;
 extern u16 ipl_devno;
 
+extern u32 dump_prefix_page;
 extern void do_reipl(void);
 extern void ipl_save_parameters(void);