[S390] kdump: Replace is_kdump_kernel() with OLDMEM_BASE check

In order to have the same behavior for kdump based stand-alone dump
as for the kexec method, the is_kdump_kernel() check (only true for
the kexec method) has to be replaced by the OLDMEM_BASE check (true
for both methods).
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/setup.c

@@ -579,7 +579,7 @@ static unsigned long __init find_crash_base(unsigned long crash_size,
 		*msg = "first memory chunk must be at least crashkernel size";
 		return 0;
 	}
-	if (is_kdump_kernel() && (crash_size == OLDMEM_SIZE))
+	if (OLDMEM_BASE && crash_size == OLDMEM_SIZE)
 		return OLDMEM_BASE;
 
 	for (i = MEMORY_CHUNKS - 1; i >= 0; i--) {