video: fix up versatile CLCD helper move

commit 11c32d7b ("video: move Versatile CLCD helpers")
moved files out of the plat-versatile directory but in the process
got a few of the dependencies wrong:

- If CONFIG_FB is not set, the file no longer gets built, resulting
  in a link error
- If CONFIG_FB or CONFIG_FB_ARMCLCD are disabled, we also get a
  Kconfig warning for incorrect dependencies due to the symbol
  being 'select'ed from the platform Kconfig.
- When the file is not built, we also get a link error for missing
  symbols.

This patch should fix all three, by removing the 'select' statements,
changing the Kconfig description of the symbol to be enabled in
exactly the right configurations, and adding inline stub functions
for the case when the framebuffer driver is disabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>