spi: uniphier: Fix a bug that doesn't point to private data correctly

In uniphier_spi_remove(), there is a wrong code to get private data from
the platform device, so the driver can't be removed properly.

The driver should get spi_master from the platform device and retrieve
the private data from it.

Cc: <stable@vger.kernel.org>
Fixes: 5ba155a4

 ("spi: add SPI controller driver for UniPhier SoC")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://lore.kernel.org/r/1640148492-32178-1-git-send-email-hayashi.kunihiko@socionext.com


Signed-off-by: Mark Brown <broonie@kernel.org>