anv: let anv_entrypoints_gen.py generate proper Wayland/Xcb guards
The generated sources should follow the example set by the vulkan
headers and our non-generated code. Namely: the code for all supported
platforms should be available, each one guarded by its respective
VK_USE_PLATFORM_*_KHR macro.
v2: Reword commit message.
Cc: Mark Janes <mark.a.janes@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96285
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net> (v1 over IRC)