Simplify tilegx sysdeps folder

With tilepro support removal we can now simplify internal tile support by
moving the directory structure to avoid the unnecessary directory levels
in tile/tilegx both on generic and linux folders.

Checked with a build for tilegx-linux-gnu and tilegx-linux-gnu-32 with
and without the patch, there is no difference in generated binary with
a dissassemble.

	* stdlib/bug-getcontext.c (do_test): Remove tilepro mention in
	comment.
	* sysdeps/tile/preconfigure: Remove tilegx folder.
	* sysdeps/tile/tilegx/Implies: Move definitions to ...
	* sysdeps/tile/Implies: ... here.
	* sysdeps/tile/tilegx/Makefile: Move rules to ...
	* sysdeps/tile/Makefile: ... here.
	* sysdeps/tile/tilegx/atomic-machine.h: Move definitions to ...
	* sysdeps/tile/atomic-machine.h: ... here.  Add include guards.
	* sysdeps/tile/tilegx/bits/wordsize.h: Move to ...
	* sysdeps/tile/bits/wordsize.h: ... here.
	* sysdeps/tile/tilegx/*: Move to ...
	* sysdeps/tile/*: ... here.
	* sysdeps/tile/tilegx/tilegx32/Implies: Move to ...
	* sysdeps/tile/tilegx32/Implies: ... here.
	* sysdeps/tile/tilegx/tilegx64/Implies: Move to ...
	* sysdeps/tile/tilegx64/Implies: ... here.
	* sysdeps/unix/sysv/linux/tile/tilegx/Makefile: Move definitions
	to ...
	* sysdeps/unix/sysv/linux/tile/Makefile: ... here.
	* sysdeps/unix/sysv/linux/tile/tilegx/*: Move to ...
	* sysdeps/unix/sysv/linux/tile/*: ... here.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/*: Move to ...
	* sysdeps/unix/sysv/linux/tile/tilegx32/*: ... here.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/*: Move to ...
	* sysdeps/unix/sysv/linux/tile/tilegx64/*: ... here.