Dialer: truncate hint text for search box

There's not enough space on hdpi if voice search is enabled.
Showing truncated text is better than showing truncated 2 lines.

Before: http://imgur.com/aSUJm7X
After: http://imgur.com/LthsLsh

Change-Id: I2f140b2e61d575ea0c745bd95eb48b9950602316