[S390] add support for compressed kernels

Add the "bzImage" compile target and the necessary code  to generate
compressed kernel images. The old style uncompressed "image" target
is preserved, a simple make will build them both.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 4033487..19deda8 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -98,6 +98,9 @@
 	select HAVE_ARCH_TRACEHOOK
 	select INIT_ALL_POSSIBLE
 	select HAVE_PERF_EVENTS
+	select HAVE_KERNEL_GZIP
+	select HAVE_KERNEL_BZIP2
+	select HAVE_KERNEL_LZMA
 	select ARCH_INLINE_SPIN_TRYLOCK
 	select ARCH_INLINE_SPIN_TRYLOCK_BH
 	select ARCH_INLINE_SPIN_LOCK