elm_interface_scrollable: fix using wrong variable.

Summary:
vy isn't initialized when p >1.0 or p<0.

this function is for finding out a current animating speed of momentum scrolling.
and a caller of this function calls this function by reference(vx, vy)
so that if progress ratio is not between 0 and 1, vx, vy must be zero.

The issue was detected by coverity check.
It may not discovered any issues yet, but the typo is too obvious, so need to fix the right value.

Test Plan: This is coverity issue.

Reviewers: akanad, Hermet, SanghyeonLee

Subscribers: segfaultxavi, cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7114

src/lib/elementary/elm_interface_scrollable.c

@@ -2605,7 +2605,7 @@ _elm_scroll_running_momentum_speed_get(Elm_Scrollable_Smart_Interface_Data *sid,
    if ( p > 1.0 || p < 0)
      {
         if (vx) *vx = 0;
-        if (vy) *vx = 0;
+        if (vy) *vy = 0;
         return EINA_FALSE;
      }