i2c: gpio: merge two very similar comments

I think it is clear enough if we have the explanation once and make it
clear it is applicable for both SCL and SDA. Reword it a little with
the help of Simon's native language skills :)

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>