spi: spi-ep93xx: pass the spi_master pointer around

Change the parameters for some of the functions so that the spi_master
pointer is passed around instead of the private data ep93xx_spi pointer.

This allows removing the 'pdev' member of the private data and will
help with some later cleanup.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Mark Brown <broonie@kernel.org>