[S390] Change default IPL method to IPL_VM.

allyesconfig and allmodconfig built kernels have a tape IPL record.
A the vmreader record makes much more sense, since hardly anybody will
ever IPL a kernel from tape. So change the default.
As I side effect I can test these kernels without fiddling around with
the kernel config ;)
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -384,7 +384,7 @@ config IPL
 choice
 	prompt "IPL method generated into head.S"
 	depends on IPL
-	default IPL_TAPE
+	default IPL_VM
 	help
 	  Select "tape" if you want to IPL the image from a Tape.