KVM: Fix instruction size issue in pvclock scaling

Commit de2d1a52 ("KVM: Fix register corruption in pvclock_scale_delta")
introduced a mul instruction that may have only a memory operand; the
assembler therefore cannot select the correct size:

   pvclock.s:229: Error: no instruction mnemonic suffix given and no register
operands; can't size instruction

In this example the assembler is:

         #APP
         mul -48(%rbp) ; shrd $32, %rdx, %rax
         #NO_APP

A simple solution is to use mulq.
Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/pvclock.h

@@ -44,7 +44,7 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
 		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
 #elif defined(__x86_64__)
 	__asm__ (
-		"mul %[mul_frac] ; shrd $32, %[hi], %[lo]"
+		"mulq %[mul_frac] ; shrd $32, %[hi], %[lo]"
 		: [lo]"=a"(product),
 		  [hi]"=d"(tmp)
 		: "0"(delta),