m68k: Fix assembler constraint to prevent overeager gcc optimisation

Passing the address of a variable as an operand to an asm statement
doesn't mark the value of this variable as used, so gcc may optimize its
initialisation away.  Fix this by using the "m" constraint instead.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org

arch/m68k/kernel/process_mm.c

@@ -189,8 +189,8 @@ void flush_thread(void)
 	current->thread.fs = __USER_DS;
 	if (!FPU_IS_EMU)
 		asm volatile (".chip 68k/68881\n\t"
-			      "frestore %0@\n\t"
-			      ".chip 68k" : : "a" (&zero));
+			      "frestore %0\n\t"
+			      ".chip 68k" : : "m" (zero));
 }
 
 /*