x86/entry, x86/paravirt: Remove the unused usergs_sysret32 PV op

As result of commit "x86/xen: Avoid fast syscall path for Xen PV
guests", usergs_sysret32 pv op is not called by Xen PV guests
anymore and since they were the only ones who used it we can
safely remove it.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1447970147-1733-4-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/xen/xen-asm_64.S

@@ -68,25 +68,6 @@ ENTRY(xen_sysret64)
 ENDPATCH(xen_sysret64)
 RELOC(xen_sysret64, 1b+1)
 
-ENTRY(xen_sysret32)
-	/*
-	 * We're already on the usermode stack at this point, but
-	 * still with the kernel gs, so we can easily switch back
-	 */
-	movq %rsp, PER_CPU_VAR(rsp_scratch)
-	movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
-
-	pushq $__USER32_DS
-	pushq PER_CPU_VAR(rsp_scratch)
-	pushq %r11
-	pushq $__USER32_CS
-	pushq %rcx
-
-	pushq $0
-1:	jmp hypercall_iret
-ENDPATCH(xen_sysret32)
-RELOC(xen_sysret32, 1b+1)
-
 /*
  * Xen handles syscall callbacks much like ordinary exceptions, which
  * means we have: