spi: dw: Move runtime PM enable/disable from common to platform driver part

spi: dw: Move runtime PM enable/disable from common to platform driver part

After commit 1e6959832510 ("spi: dw: Add basic runtime PM support")
there is following warning from PCI enumerated DesignWare SPI controller
during probe:

	dw_spi_pci 0000:00:13.0: Unbalanced pm_runtime_enable!

Runtime PM is already enabled for PCI devices by the PCI core and doing
it again in common DW SPI code leads to unbalanced enable calls.

Fix this by moving the runtime PM enable/disable calls to the platform
driver part of the driver.

Cc: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20191018132131.31608-1-jarkko.nikula@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>