ide: remove obsoleted "idebus=" kernel parameter

* Remove obsoleted "idebus=" kernel parameter.

* Remove no longer needed ide_system_bus_speed() and system_bus_clock()
  (together with idebus_parameter and system_bus_speed variables).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/legacy/ht6560b.c b/drivers/ide/legacy/ht6560b.c
index 4fe516d..dd6dfb3 100644
--- a/drivers/ide/legacy/ht6560b.c
+++ b/drivers/ide/legacy/ht6560b.c
@@ -212,7 +212,7 @@
 {
 	int active_time, recovery_time;
 	int active_cycles, recovery_cycles;
-	int bus_speed = ide_vlb_clk ? ide_vlb_clk : system_bus_clock();
+	int bus_speed = ide_vlb_clk ? ide_vlb_clk : 50;
 
         if (pio) {
 		unsigned int cycle_time;