i2c: reword i2c_algorithm according to newest specification

Start changing the wording of the I2C main header wrt. the newest I2C
v7 and SMBus 3.2 specifications and replace "master/slave" with more
appropriate terms. The first step renames the members of struct
i2c_algorithm. Once all in-tree users are converted, the anonymous union
will go away again. All this work will also pave the way for finally
seperating the monolithic header into more fine-grained headers like
"i2c/clients.h" etc.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>