pkt_sched: Use PSCHED_SHIFT in PSCHED time conversion

Use PSCHED_SHIFT constant instead of '10' in PSCHED_US2NS() and
PSCHED_NS2US() macros to enable changing this value later.

Additionally use PSCHED_SHIFT in sch_hfsc SM_SHIFT and ISM_SHIFT
definitions. This part of the patch is based on feedback from
Patrick McHardy <kaber@trash.net>.

Reported-by: Antonio Almeida <vexwek@gmail.com>
Tested-by: Antonio Almeida <vexwek@gmail.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index e37fe31..cd0e026 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -42,8 +42,9 @@
 typedef long	psched_tdiff_t;
 
 /* Avoid doing 64 bit divide by 1000 */
-#define PSCHED_US2NS(x)			((s64)(x) << 10)
-#define PSCHED_NS2US(x)			((x) >> 10)
+#define PSCHED_SHIFT			10
+#define PSCHED_US2NS(x)			((s64)(x) << PSCHED_SHIFT)
+#define PSCHED_NS2US(x)			((x) >> PSCHED_SHIFT)
 
 #define PSCHED_TICKS_PER_SEC		PSCHED_NS2US(NSEC_PER_SEC)
 #define PSCHED_PASTPERFECT		0