uml: remove code made redundant by CHOOSE_MODE removal

This patch makes a number of simplifications enabled by the removal of
CHOOSE_MODE.  There were lots of functions that looked like

	int foo(args){
		foo_skas(args);
	}

The bodies of foo_skas are now folded into foo, and their declarations (and
sometimes entire header files) are deleted.

In addition, the union uml_pt_regs, which was a union between the tt and skas
register formats, is now a struct, with the tt-mode arm of the union being
removed.

It turns out that usr2_handler was unused, so it is gone.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/kernel/syscall.c

@@ -20,7 +20,6 @@
 #include "asm/uaccess.h"
 #include "kern_util.h"
 #include "sysdep/syscalls.h"
-#include "mode_kern.h"
 
 /*  Unlocked, I don't care if this is a bit off */
 int nsyscalls = 0;