cleanup and refactor lcd.c

This series is a first step towards an end goal of merging all CONFIG_LCD related functionality into CONFIG_VIDEO code. My plan is to start by refactoring lcd.c into something cleaner (less ifdefs) and more modular (split code into multiple files), then possibly refactor CONFIG_VIDEO code if needed, and then
finally: move CONFIG_LCD related functionality over to CONFIG_VIDEO code, replacing as much CONFIG_LCD related code with CONFIG_VIDEO related code as possible.

This specific step eliminates some unused code and refactors lcd console stuff into its own file.

In V2 I broke the last patch of the original series ("lcd: refactor lcd console stuff into its own file") into multiple patches to make it clear what changes had to be done in order to refactor the lcd console code into its own file. These preparatory patches ("lcd: rename console_(row|col)" to "lcd: make lcd_drawchars() independant of lcd_base") are meant to illustrate exactly what changed and where in the transition from lcd.c to lcd_console.c, and are not necesserily code improvements when viewed out of context.

Additional changes in V2:
- Added documentation for the new functions.

The whole series was rebased over current mainline, and compile tested for arm and powerpc.