i2c-eg20t : Fix the issue of Combined R/W transfer mode

issue-1
In case combined transfer mode fails halfway, the processing must be stopped halfway.
However currently, the processing is continued.
This patch breaks the processing.

issue-2
Currently, pch_i2c_xfer returns read/write size at that time.
However pch_i2c_xfer must return the number of messages to be read/written.
This patch modifies correctly.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>