Changed Grid layout on home. More space at the bottom.

Bug: http://b/issue?id=3053235

This is a proper way to do what was done in https://android-git.corp.google.com/g/#change,71522

The longAxisEndPadding used to be equal to button_bar_height.
Increased it to match proposed mock from designers and increase space
between last row and hot seats buttons.

Change-Id: I31dfba0a3e90a30f18d42b16681592d9527517d4
diff --git a/res/layout-port/workspace_screen.xml b/res/layout-port/workspace_screen.xml
index 96df91b..bd4a4bd 100644
--- a/res/layout-port/workspace_screen.xml
+++ b/res/layout-port/workspace_screen.xml
@@ -25,7 +25,7 @@
     launcher:cellWidth="@dimen/workspace_cell_width"
     launcher:cellHeight="@dimen/workspace_cell_height"
     launcher:longAxisStartPadding="8dip"
-    launcher:longAxisEndPadding="@dimen/button_bar_height"
+    launcher:longAxisEndPadding="78dip"
     launcher:shortAxisStartPadding="0dip"
     launcher:shortAxisEndPadding="0dip"
     launcher:shortAxisCells="4"