ARM: shmobile: r8a7790: lager: use iic cores instead of i2c

On Lager board, i2c and iic cores can be interchanged since they can be
muxed to the same wires. Commit e489c2a9
("ARM: shmobile: lager: enable i2c devices") activated the i2c cores,
yet the iic cores should be default since they have the more interesting
features for generic use cases, i.e. SMBUS_QUICK and DMA (yet to be
supported).

Reported-by: Khiem Nguyen <khiem.nguyen.xt@renesas.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>