[POWERPC] briq_panel Kconfig fix

drivers/char/briq_panel.c:28:22: error: asm/prom.h: No such file or directory

Cc: Jeremy Kerr <jk@ozlabs.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>