i2c: mlxcpld: Fix adapter functionality support callback

It fixes report about supported functionality.
Functionality can be different up to CPLD capability.

Fixes: 6bec23bf (i2c: mlxcpld: add master driver for mellanox systems)
Signed-off-by: Michael Shych <michaelsh@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>