anv: Allow presenting via a different GPU

anv: Allow presenting via a different GPU

anv_GetPhysicalDeviceSurfaceSupportKHR will already return success for
this, but anv_GetPhysicalDevice{Xcb,Xlib}PresentationSupportKHR do not.
Apps which check for presentation support via the latter (all Feral
Vulkan games at least) will therefore fail.

This allows me to render on an Intel GPU and present to a display
connected to an AMD card (tested HD 530 + Vega 64).

v2: Rebase on current master.

Signed-off-by: Alex Smith <asmith@feralinteractive.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>