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>
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index ec1ed68..b10ee28 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -91,7 +91,7 @@
 
 extern void free_irqs(void);
 
-void sigio_handler(int sig, union uml_pt_regs *regs)
+void sigio_handler(int sig, struct uml_pt_regs *regs)
 {
 	struct irq_fd *irq_fd;
 	int n;
@@ -344,7 +344,7 @@
  * SMP cross-CPU interrupts have their own specific
  * handlers).
  */
-unsigned int do_IRQ(int irq, union uml_pt_regs *regs)
+unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
 	irq_enter();