time: ntp: make 64-bit constants more robust

Impact: cleanup, no functionality changed

 - make PPM_SCALE an explicit s64 constant, to
   remove (s64) casts from usage sites.

kernel/time/ntp.o:

   text	   data	    bss	    dec	    hex	filename
   2536	    114	    136	   2786	    ae2	ntp.o.before
   2536	    114	    136	   2786	    ae2	ntp.o.after

md5:
   40a7728d1188aa18e83e21a81fa7b150  ntp.o.before.asm
   40a7728d1188aa18e83e21a81fa7b150  ntp.o.after.asm
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/timex.h

@@ -190,7 +190,7 @@ struct timex {
  * offset and maximum frequency tolerance.
  */
 #define SHIFT_USEC 16		/* frequency offset scale (shift) */
-#define PPM_SCALE (NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
+#define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
 #define PPM_SCALE_INV_SHIFT 19
 #define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
 		       PPM_SCALE + 1)

kernel/time/ntp.c

@@ -408,7 +408,7 @@ static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts
 		time_status &= ~STA_NANO;
 
 	if (txc->modes & ADJ_FREQUENCY) {
-		time_freq = (s64)txc->freq * PPM_SCALE;
+		time_freq = txc->freq * PPM_SCALE;
 		time_freq = min(time_freq, MAXFREQ_SCALED);
 		time_freq = max(time_freq, -MAXFREQ_SCALED);
 	}
@@ -505,7 +505,7 @@ int do_adjtimex(struct timex *txc)
 		result = TIME_ERROR;
 
 	txc->freq	   = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
-					 (s64)PPM_SCALE_INV, NTP_SCALE_SHIFT);
+					 PPM_SCALE_INV, NTP_SCALE_SHIFT);
 	txc->maxerror	   = time_maxerror;
 	txc->esterror	   = time_esterror;
 	txc->status	   = time_status;