[S390] fix "mem=" handling in case of standby memory

Standby memory detected with the sclp interface gets always registered
with add_memory calls without considering the limitationt that the
"mem=" kernel paramater implies.
So fix this and only register standby memory that is below the specified
limit.
This fixes zfcpdump since it uses "mem=32M". In case there is appr.
2GB standby memory present all of usable memory would be used for the
struct pages needed for standby memory.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/setup.h b/arch/s390/include/asm/setup.h
index 2bd9fae..e8bd6ac 100644
--- a/arch/s390/include/asm/setup.h
+++ b/arch/s390/include/asm/setup.h
@@ -43,6 +43,8 @@
 
 extern struct mem_chunk memory_chunk[];
 extern unsigned long real_memory_size;
+extern int memory_end_set;
+extern unsigned long memory_end;
 
 void detect_memory_layout(struct mem_chunk chunk[]);