i2c_master_recv() returns negative errno, or else the number of bytes
read.  Thus i2c_master_recv(client, i2c_data, 2) returns 2 instead of 1 in
success case.

[akpm@linux-foundation.org: make `ret' signed]
Signed-off-by: NAxel Lin <axel.lin@gmail.com>
Cc: Kalhan Trisal <kalhan.trisal@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>