spi: spi-geni-qcom: Modify GSI Rx transfer issue logic

In GSI mode, make the Rx channel dma_engine calls conditional to if
the current transfer being processed has any Rx related trasaction
rather than the total number of rx_eot accumulated by the master for
a given message.
This will impact cases where a message does a full-duplex transfer
followed by a half-duplex Tx only transfer.

Change-Id: I81a170451299011313277fd9af9e1118bb001ec0
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>