Fix build warning when built as a loadable module.
amifb_setup() and amifb_setup_mcap() are only needed when the driver
is builtin.
This matches how the functions are called (using #ifndef MODULE).
../drivers/video/fbdev/amifb.c:2344:19: warning: 'amifb_setup' defined but not used [-Wunused-function]
static int __init amifb_setup(char *options)
../drivers/video/fbdev/amifb.c:2307:20: warning: 'amifb_setup_mcap' defined but not used [-Wunused-function]
static void __init amifb_setup_mcap(char *spec)