Replaced get_tick_per_sec() by NANOSECONDS_PER_SECOND

This patch replaces get_ticks_per_sec() calls with the macro
NANOSECONDS_PER_SECOND. Also, as there are no callers, get_ticks_per_sec()
is then removed.  This replacement improves the readability and
understandability of code.

For example,

    timer_mod(fdctrl->result_timer,
	      qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + (get_ticks_per_sec() / 50));

NANOSECONDS_PER_SECOND makes it obvious that qemu_clock_get_ns
matches the unit of the expression on the right side of the plus.

Signed-off-by: Rutuja Shah <rutu.shah.26@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/backends/baum.c b/backends/baum.c
index f95f7be..c537141 100644
--- a/backends/baum.c
+++ b/backends/baum.c
@@ -337,7 +337,7 @@
 
         /* Allow 100ms to complete the DisplayData packet */
         timer_mod(baum->cellCount_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
-                       get_ticks_per_sec() / 10);
+                       NANOSECONDS_PER_SECOND / 10);
         for (i = 0; i < baum->x * baum->y ; i++) {
             EAT(c);
             cells[i] = c;