Attempts to build with CONFIG_ADF_MEMBLOCK=m result in the following
build error.
ERROR: "memblock_free" [drivers/video/adf/adf_memblock.ko] undefined!
memblock_free() is marked as __init_memblock, so exporting it seems to be
a bad idea. All other callers are only configurable into the kernel,
so do the same with ADF_MEMBLOCK.
Signed-off-by: Guenter Roeck <groeck@chromium.org>