regulator: tps6524x: Fix broken use of spi_dev_get()

The tps6524x driver uses spi_dev_get() to take a copy of the SPI device
it uses but has no obvious reason to do so and never calls spi_dev_put()
to release the reference.  Fix this to just a straight copy.

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