don't save eflags in x86-64 switch_to()

From: Benjamin LaHaise <bcrl@kvack.org>

As discussed, the flags register on x86-64 is saved and restored by the 
assembly code which sets up struct pt_regs, so we do not need to save 
and restore it in the inline assembler which already informs gcc that 
we're clobbering the flags.  This patch has been sanity booted and works 
okay here.

Signed-off-by: Benjamin LaHaise <benjamin.c.lahaise@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>

diff --git a/include/asm-x86_64/system.h b/include/asm-x86_64/system.h
index 85348e0..aa5abb0 100644
Index: linux/include/asm-x86_64/system.h
===================================================================
--- linux.orig/include/asm-x86_64/system.h
+++ linux/include/asm-x86_64/system.h
@@ -20,8 +20,8 @@
 #define __RESTORE(reg,offset) "movq (14-" #offset ")*8(%%rsp),%%" #reg "\n\t"
 
 /* frame pointer must be last for get_wchan */
-#define SAVE_CONTEXT    "pushfq ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"
-#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popfq\n\t" 
+#define SAVE_CONTEXT    "pushq %%rbp ; movq %%rsi,%%rbp\n\t"
+#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp\n\t"
 
 #define __EXTRA_CLOBBER  \
 	,"rcx","rbx","rdx","r8","r9","r10","r11","r12","r13","r14","r15"