configs/qemu_s390x_defconfig: use linux headers same as kernel series 5.8

Broke since introduction of linux kernel series 5.9.

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

configs/qemu_s390x_defconfig

@@ -11,6 +11,9 @@ BR2_ROOTFS_POST_SCRIPT_ARGS="$(BR2_DEFCONFIG)"
 BR2_TARGET_ROOTFS_EXT2=y
 # BR2_TARGET_ROOTFS_TAR is not set
 
+# Linux headers same as kernel, a 5.8 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_8=y
+
 # Kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y