[PATCH] i2c: writing-client doc update complement

My latest update to the writing-clients i2c documentation file was
incomplete, here's the complement.

Large parts of this file are still way out-of-date, but at least now
the memory allocation and freeing instructions are consistent.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>