Revert "s390/mem_detect: do not update output parameters on failure"

This reverts commit cbc29f10.

Get rid of the following smatch warnings:

arch/s390/include/asm/mem_detect.h:86 get_mem_detect_end() error: uninitialized symbol 'end'.
arch/s390/include/asm/mem_detect.h:86 get_mem_detect_end() error: uninitialized symbol 'end'.
arch/s390/boot/vmem.c:256 setup_vmem() error: uninitialized symbol 'start'.
arch/s390/boot/vmem.c:258 setup_vmem() error: uninitialized symbol 'end'.

Note that there is no bug in the code. This is purely to silence smatch.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/mem_detect.h

@@ -40,8 +40,11 @@ void add_mem_detect_block(u64 start, u64 end);
 static inline int __get_mem_detect_block(u32 n, unsigned long *start,
 					 unsigned long *end)
 {
-	if (n >= mem_detect.count)
+	if (n >= mem_detect.count) {
+		*start = 0;
+		*end = 0;
 		return -1;
+	}
 
 	if (n < MEM_INLINED_ENTRIES) {
 		*start = (unsigned long)mem_detect.entries[n].start;