staging: comedi: ni_at_a2150: sample types are unsigned

Sample values in comedi are generally represented by unsigned values.
Change the type of the `dma_buffer` member of `struct a2150_private`
from `s16 *` to `uint16_t *`, and change the type of the `dpnt` variable
in `a2150_interrupt()` to `unsigned short` for consistency.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/ni_at_a2150.c

@@ -154,7 +154,7 @@ struct a2150_private {
 
 	volatile unsigned int count;	/* number of data points left to be taken */
 	unsigned int dma;	/*  dma channel */
-	s16 *dma_buffer;	/*  dma buffer */
+	uint16_t *dma_buffer;	/*  dma buffer */
 	unsigned int dma_transfer_size;	/*  size in bytes of dma transfers */
 	int irq_dma_bits;	/*  irq/dma register bits */
 	int config_bits;	/*  config register bits */
@@ -192,7 +192,7 @@ static irqreturn_t a2150_interrupt(int irq, void *d)
 	struct comedi_async *async;
 	struct comedi_cmd *cmd;
 	unsigned int max_points, num_points, residue, leftover;
-	short dpnt;
+	unsigned short dpnt;
 	static const int sample_size = sizeof(devpriv->dma_buffer[0]);
 
 	if (!dev->attached) {