Allow adb shell am display-size to use bigger sizes.

We now support scaling the logical display to fit the
physical display, whatever size it is.  So we can allow
adb shell am display-size to use more or less arbitrary sizes
although we do enforce an upper and lower bound to
protect the user.

Change-Id: I5fe6ba32ad1f9e4fbcd6915f7d36850b987bbcc0