Revert "busybox: init: remove usleep"

usleep is used by init's functions to create quarter and half second
progress reports. Not worth diving into for what was a 1.2kb savings.

This reverts commit 9e055544be.

packages/sysutils/busybox/scripts/init

@@ -111,7 +111,7 @@ mount_common() {
     mount $MOUNT_OPTIONS $1 $2 >&$SILENT_OUT 2>&1
     [ "$?" -eq "0" ] && ERR_ENV=0 && break
 
-    sleep 1
+    usleep 1000000
   done
   [ "$ERR_ENV" -eq "0" ] && return 0
   error "mount_common" "Could not mount $1"
@@ -442,7 +442,7 @@ do_reboot() {
     /usr/bin/busybox umount /storage
   fi
 
-  sleep 2
+  usleep 2000000
   /usr/bin/busybox reboot
 }
 
@@ -496,7 +496,7 @@ check_disks() {
         if [ $i -eq 0 ]; then
           progress "Device not found, continuing..."
         else
-          sleep 1
+          usleep 500000
         fi
       elif [ $(( $FSCK_RET & 4 )) -eq 4 ]; then
         # errors left