staging: sm7xxfb: clean fb_fix_screeninfo and fb_var_screeninfo initialization

Part of fb_fix_screeninfo and fb_var_screeninfo initialization happens
in smtc_alloc_fb_info. It duplicates code while hiding the real
functionality of smtc_alloc_fb_info. This patch groups initialization
together.

Signed-off-by: Javier M. Mellid <jmunhoz@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>