spi: spi_qsd: Use the right device for dma_unmap_single operation

The unmap operation of a dma bounce buffer is performed using an incorrect
device compared to the map operation. This leads to a leaked bounce buffer
dma map.

Fix the device usage during the unmap operation.

CRs-Fixed: 1104864
Change-Id: I7da2484ce1f070a4545b9110e3602b4f39d7afdc
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>