ASoC: qcom: rename rdma_ch_bit_map to dma_ch_bit_map

rdma_ch_bit_map can be reused for wrdma channel allocations as wrdma
channel numbering start after rdma channel numbers.
With capture support referring rdma_ch_bit_map for wrdma channel allocation
is confusing, so renaming rdma_ch_bit_map to dma_ch_bit_map makes sense.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>