i2c: i2c-qcom-geni: Simplify tx/rx functions

We never really look at the 'ret' local variable in these functions, so
let's remove it to make way for shorter and simpler code. Furthermore,
we can shorten some lines by adding two local variables for the SE and
the message length so that everything fits in 80 columns and testing the
'dma_buf' local variable in lieu of the 'mode' local variable.  And
kernel style is to leave the return statement by itself, detached from
the rest of the function.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Alok Chauhan <alokc@codeaurora.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>