i2c: i2c-msm-geni: Avoid usage of dma chan_id in case of GSI transfer

DMA chan_id is different than GSI GPII channel id, instead check for
whether it's tx or rx channel directly in prepare descriptor api.

Change-Id: Ia5758ddeef89c3ee69e23a5b4ea2117ec45d44a5
Signed-off-by: Vipin Deep Kaur <vkaur@codeaurora.org>