headers: GH7, Fix bad variable names in vk_icd.h
headers: GH7, Fix bad variable names in vk_icd.h

Change-Id: Ic78792a71ebedbdb5bae68c47856db1c89a714af

KhronosGroup/Vulkan-Headers,KhronosGroup/Vulkan-Headers,KhronosGroup/Vulkan-Headers