Fix KHR-GL45/46.enhanced_layouts.varying_block_member_locations

Fix KHR-GL45/46.enhanced_layouts.varying_block_member_locations

The stages of the same program used in/out blocks that didn't match
(see section 4.7.1 in OpenGL 4.5 spec: qualification mismatch) and as a
result a linker error was produced. With this change all stages use the
same block definition which is either the 1st or the 2nd depending on
the iteration but not both at the same time:

Goku {
    vec4 gohan;
    vec4 goten;
    vec4 chichi;
} gokuARRAY;

Goku {
    layout (location = 2) vec4 gohan;
    layout (location = 4) vec4 goten;
    layout (location = 6) vec4 chichi;
} gokuARRAY;

Affects:

KHR-GL46.enhanced_layouts.varying_block_member_locations
KHR-GL45.enhanced_layouts.varying_block_member_locations

Components: OpenGL

VK-GL-CTS issue: 703

Change-Id: I03a6a90929e28489a2507838003c62475a8a58b8
(cherry picked from commit 4b6462e469359ac7ddec9c63d042e43ead6031fc)