platform: Correct the max character number shown per line

The number of max character shown per line is decided by the
screen's width, height and factor. So update the code to get
the number dynamically. Otherwise maybe cause the Y-axis is
over than Y-max during drawing menu

1. Add support for horizontal orientation display.
2. Correct the character number for per line.

Change-Id: Icd691acaca5091aaae8fe88491d4700e42c78e9b