nto & lynx x86: call init_target_desc

nto & lynx x86: call init_target_desc

In gdbserver, target descriptions need to be initialized by calling
init_target_desc.  Because i386_create_target_description is shared with
GDB, it doesn't do that, the callers must take care of it.  These two
platforms currently don't.

I am not able to build them, so I couldn't test.

gdb/gdbserver/ChangeLog:

	* lynx-i386-low.c (lynx_i386_arch_setup): Call init_target_desc.
	* nto-x86-low.c (nto_x86_arch_setup): Likewise.