loader: Only create gfx 4th bindings when gfx is available

[imp]

Summary

Only create the gfx bindings for 4th when it's comiled into the
kernel. We do this with a linker set that only gets brought in to those
loaders that call gfx_framework_init. This calls gfx_interp_md() will
will drag in gfx_loader.c which will add to the linker set that
registers these bindings.

Sponsored by: Netflix

[jhb]

s/comile/compile/ in the commit log, and I think you want s/kernel/loader/ in the commit log as well

[imp]

In D43904#1001560, @jhb wrote:

s/comile/compile/ in the commit log, and I think you want s/kernel/loader/ in the commit log as well

Updated, thanks!