i2c: qcom-cci: simplify access to bus data structure

Trivial non-functional change, which adds an alias to an extensively
used data location.

Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>