radeon_hd: move some atombios headers to private/graphics

These will be needed to implement custom modes in the VESA driver.

Change-Id: I9b52de691baa14e1f1a3ccce500ced9bb040b113
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4622
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

src/add-ons/accelerants/radeon_hd/Jamfile

@@ -5,6 +5,7 @@ SEARCH_SOURCE += [ FDirName $(HAIKU_TOP) src add-ons accelerants radeon_hd atomb
 UseHeaders [ FDirName $(SUBDIR) atombios ] ;
 UsePrivateHeaders graphics ;
 UsePrivateHeaders [ FDirName graphics radeon_hd ] ;
+UsePrivateHeaders [ FDirName graphics radeon_hd atombios ] ;
 UsePrivateHeaders [ FDirName graphics common ] ;
 UsePrivateHeaders shared ;