gpu: host1x: Make host1x header file public

In preparation to support host1x clients other than DRM, move this
header into a public location.

Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 284969f..89f347a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2817,6 +2817,7 @@
 T:	git git://anongit.freedesktop.org/tegra/linux.git
 S:	Maintained
 F:	drivers/gpu/host1x/
+F:	include/linux/host1x.h
 F:	include/uapi/drm/tegra_drm.h
 F:	Documentation/devicetree/bindings/gpu/nvidia,tegra20-host1x.txt