common/lcd.c: remove global lcd_base

lcd_base is available as gd->fb_base as well, there is no need
to keep a seperate copy.

For completeness the ack of Bo Shen is for the atmel part.
Cc: Alessandro Rubini <rubini@unipv.it>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Bo Shen <voice.shen@atmel.com>
Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Nikita Kiryanov <nikita@compulab.co.il>
Cc: Simon Glass <sjg@chromium.org>
Cc: Stelian Pop <stelian@popies.net>
Cc: Tom Warren <twarren@nvidia.com>
Acked-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>
[agust: also fix cm_t35 board while rebasing]
Signed-off-by: Anatolij Gustschin <agust@denx.de>