arm: fix implicit use of sched.h in bcmring/dma.c

To fix this:

arch/arm/mach-bcmring/dma.c: In function 'dma_request_channel_dbg':
arch/arm/mach-bcmring/dma.c:1022: error: 'TASK_INTERRUPTIBLE' undeclared (first use in this function)
arch/arm/mach-bcmring/dma.c:1022: error: (Each undeclared identifier is reported only once

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

arch/arm/mach-bcmring/dma.c

@@ -26,6 +26,7 @@
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
+#include <linux/sched.h>
 #include <linux/irqreturn.h>
 #include <linux/proc_fs.h>
 #include <linux/slab.h>