i2c: wmt: add platform type VIAI2C_PLAT_WMT

Enumeration variables are added to differentiate
between different platforms.

Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Hans Hu <hanshu-oc@zhaoxin.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>