gpu: ion: Remove incorrect error message

The function name is wrong here, and this function may
sometimes be called to see if a value passed from userspace
is an ion handle.  Since it's not really an error when it
fails, remove the log message.

Change-Id: I7bee0e7ffb72b4c4768774a3586f97e306700c21
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>