Fix compilation of dsp_mem.c. omapfb_ready is only available if
CONFIG_FB_OMAP_LCDC_EXTERNAL is set, else compiler stops with error.
status is only used in case CONFIG_FB_OMAP_LCDC_EXTERNAL is set.
Compiler warns about this.
Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>