i2c: viperboard: return message count on master_xfer success

Returning zero is wrong in this case.

Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Fixes: 174a13aa8669 ("i2c: Add viperboard i2c master driver")
1 file changed