backend/drm: stop using drm_surface_make_current in drm_surface_blit
backend/drm: stop using drm_surface_make_current in drm_surface_blit

drm_surface_make_current and drm_surface_unset_current set implicit
state and are an unnecessary mid-layer. Prefer to use directly
wlr_renderer_begin_with_buffer, which automatically unsets the back
buffer on wlr_renderer_end.

I'd like to get rid of drm_surface_make_current once we stop using
it for the primary swapchain.

SirCmpwn/wlroots,swaywm/wlroots,swaywm/wlroots