s390/crashdump: remove unused variable

Get rid of this compile warning:

arch/s390/kernel/crash_dump.c: In function 'copy_from_realmem':
arch/s390/kernel/crash_dump.c:48:6: warning: unused variable 'rc'
[-Wunused-variable]
  int rc;
      ^
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/crash_dump.c

@@ -45,7 +45,6 @@ static inline void *load_real_addr(void *addr)
 static int copy_from_realmem(void *dest, void *src, size_t count)
 {
 	unsigned long size;
-	int rc;
 
 	if (!count)
 		return 0;