s390: Add KERNEL_IMAGE_BASE to kasan.config

s390: Add KERNEL_IMAGE_BASE to kasan.config

Although Kconfig specifies:

config KERNEL_IMAGE_BASE
        hex "Kernel image base address"
        range 0x100000 0x1FFFFFE0000000 if !KASAN
        range 0x100000 0x1BFFFFE0000000 if KASAN
        default 0x3FFE0000000 if !KASAN
        default 0x7FFFE0000000 if KASAN

Running make defconfig or make debug_defconfig
followed by make kasan.config results in a suboptimal
CONFIG_KERNEL_IMAGE_BASE=0x3FFE0000000. Add
CONFIG_KERNEL_IMAGE_BASE=0x7FFFE0000000 to kasan.config to address that.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>