KVM: arm/arm64: vgic: constify seq_operations and file_operations

vgic_debug_seq_ops and file_operations are not supposed to change
at runtime and none of the structures is modified.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>