vulkan/wsi: Fix -Wreturn-type warning
This was probably a typo? There are no other instances of X11_SUPPORT
so this should presumably be XCB_SUPPORT
which is defined in the meson.build
.
Fixes a warning when wayland is disabled.
../mesa-progs-9999/src/vulkan/wsi/wsi.c:38:1: error: control reaches end of non-void function [-Werror=return-type]