x86/entry: Convert Stack segment exception to IDTENTRY

Convert #SS to IDTENTRY_ERRORCODE:
  - Implement the C entry point with DEFINE_IDTENTRY
  - Emit the ASM stub with DECLARE_IDTENTRY
  - Remove the ASM idtentry in 64bit
  - Remove the open coded ASM entry code in 32bit
  - Fixup the XEN/PV code
  - Remove the old prototypes

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134905.539867572@linutronix.de

arch/x86/kernel/idt.c

@@ -81,7 +81,7 @@ static const __initconst struct idt_data def_idts[] = {
 	INTG(X86_TRAP_OLD_MF,		asm_exc_coproc_segment_overrun),
 	INTG(X86_TRAP_TS,		asm_exc_invalid_tss),
 	INTG(X86_TRAP_NP,		asm_exc_segment_not_present),
-	INTG(X86_TRAP_SS,		stack_segment),
+	INTG(X86_TRAP_SS,		asm_exc_stack_segment),
 	INTG(X86_TRAP_GP,		general_protection),
 	INTG(X86_TRAP_SPURIOUS,		spurious_interrupt_bug),
 	INTG(X86_TRAP_MF,		coprocessor_error),