Correct support conditions for float16s

Correct support conditions for float16s

My previous fix missed out the graphics versions of these tests, so add
the correct conditions under which these tests can be supported as well.

Components: Vulkan
VK-GL-CTS issue: 1499
Affects:
dEQP-VK.spirv_assembly.instruction.compute.float16.opconstantcomposite.*
dEQP-VK.spirv_assembly.instruction.graphics.opspecconstantop.fconvert16_*
dEQP-VK.spirv_assembly.instruction.graphics.float16.opconstant.*

Change-Id: I7ac48027b4160bd82484e7d8d780d8a1870babbf
(cherry picked from commit f2ed80c3d2f8b4f2e782f71cc3755fe06ab52b33)