Staging: comedi: Fix unsigned return type

In each case, the function has an unsigned return type, but returns a
negative constant to indicate an error condition.  For move_block_from_dma,
there is only one call and the return value is dropped, so it need not be
unsigned.  For labpc_eeprom_write, there is only one call and the result is
stored in a signed variable, so again the unsigned return type is not
necessary.

A sematic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@exists@
identifier f;
constant C;
@@

 unsigned f(...)
 { <+...
*  return -C;
 ...+> }
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/drivers/adl_pci9118.c

@@ -634,7 +634,7 @@ static unsigned int defragment_dma_buffer(struct comedi_device *dev,
 /*
 ==============================================================================
 */
-static unsigned int move_block_from_dma(struct comedi_device *dev,
+static int move_block_from_dma(struct comedi_device *dev,
 					struct comedi_subdevice *s,
 					short *dma_buffer,
 					unsigned int num_samples)

drivers/staging/comedi/drivers/ni_labpc.c

@@ -250,7 +250,7 @@ static unsigned int labpc_serial_in(struct comedi_device *dev);
 static unsigned int labpc_eeprom_read(struct comedi_device *dev,
 				      unsigned int address);
 static unsigned int labpc_eeprom_read_status(struct comedi_device *dev);
-static unsigned int labpc_eeprom_write(struct comedi_device *dev,
+static int labpc_eeprom_write(struct comedi_device *dev,
 				       unsigned int address,
 				       unsigned int value);
 static void write_caldac(struct comedi_device *dev, unsigned int channel,
@@ -1986,8 +1986,8 @@ static unsigned int labpc_eeprom_read(struct comedi_device *dev,
 	return value;
 }
 
-static unsigned int labpc_eeprom_write(struct comedi_device *dev,
-				       unsigned int address, unsigned int value)
+static int labpc_eeprom_write(struct comedi_device *dev,
+				unsigned int address, unsigned int value)
 {
 	const int write_enable_instruction = 0x6;
 	const int write_instruction = 0x2;