commit cedbecd6 upstream.

Add -fno-delete-null-pointer-checks to CFLAGS for the code in
arch/s390/boot. Without the option a compressed kernel built with
gcc 4.9 won't boot.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>