spi: cadence-quadspi: Fix indirect write timeout when DMA read mode is enabled

spi: cadence-quadspi: Fix indirect write timeout when DMA read mode is enabled

When use_dma_read is enabled, the IRQ handler unconditionally overwrites
irq_status with the return value of get_dma_status(). For write operations,
DMA status returns 0 since no DMA read is in progress, causing irq_status
to become 0. The subsequent completion signal is never triggered and the
write operation times out with -ETIMEDOUT:

  cadence-qspi f1010000.spi: Indirect write timeout
  spi-nor spi0.1: operation failed with -110

Fix this by separating the DMA completion path from the write interrupt
path. If get_dma_status() indicates DMA read completion, signal completion
and return immediately. Otherwise, preserve the original irq_status so that
write completion interrupts are correctly recognized and signalled.

Fixes: aac733a96636 ("spi: cadence-qspi: Fix style and improve readability")
Signed-off-by: Srikanth Boyapally <srikanth.boyapally@amd.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Link: https://patch.msgid.link/20260708045148.2993313-1-srikanth.boyapally@amd.com
Signed-off-by: Mark Brown <broonie@kernel.org>