mfd: Remove support for early drop ab8500 chip

This patch removes the early drop version of ab8500 which have
the really bad version nr 0x0. This chip should not be found in
the wild and only exist as ST-Ericsson scrap equipment.

Signed-off-by: Mattias Wallin <mattias.wallin@stericsson.com>
Reviewed-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>