ARM: multi_v7_defconfig: Enable SECCOMP

Systemd already supports seccomp.  It seems some distros are building
systemd with seccomp, e.g. Arch on ARM, thus leading to boot errors:

systemd-logind.service: Failed at step SECCOMP spawning /usr/lib/systemd/systemd-logind: Invalid argument
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>

arch/arm/configs/multi_v7_defconfig

@@ -126,6 +126,7 @@ CONFIG_SMP=y
 CONFIG_NR_CPUS=16
 CONFIG_HIGHPTE=y
 CONFIG_CMA=y
+CONFIG_SECCOMP=y
 CONFIG_ARM_APPENDED_DTB=y
 CONFIG_ARM_ATAG_DTB_COMPAT=y
 CONFIG_KEXEC=y