spi: fsl-dspi: fix wrong pointer in suspend/resume

spi: fsl-dspi: fix wrong pointer in suspend/resume

Since commit 81313147de75 ("spi: fsl-dspi: fix use-after-free in
remove path"), this driver causes a "NULL pointer dereference"
in dspi_suspend/resume.
This is because since this commit, the drivers private data point to
"dspi" instead of "ctlr", the codes in suspend and resume func were
not modified correspondly.

Fixes: 81313147de75 ("spi: fsl-dspi: fix use-after-free in remove path")
Signed-off-by: Zhao Qiang <qiang.zhao@nxp.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20201103020546.1822-1-qiang.zhao@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>