Fix GCC 7 implicit fallthrough warnings

Fix GCC 7 implicit fallthrough warnings

GCC 7 with -Wextra or -Wimplicit-fallthrough enabled warns when
a switch case falls through. For cases where this is intentional
the warning can be suppressed with a comment. Breaks and returns
were also added for cases which end in DE_FATAL.

Removing a fallthrough in vktSparseResourcesShaderIntrinsics.cpp
resulted in new test cases.

Affects: *

New tests:
dEQP-VK.sparse_resources.shader_intrinsics.3d_sparse_fetch.*

Components: Framework, Vulkan, OpenGL

VK-GL-CTS issue: 1067

Change-Id: I0306f96cf3a50e85144b4dd22a9a88cd908607d3