staging: speakup: selection: replace _manual_ swap with swap macro

staging: speakup: selection: replace _manual_ swap with swap macro

Make use of the swap macro instead of _manually_ swapping values
and remove unnecessary variable tmp.

This makes the code easier to read and maintain.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>