rockchip: spi: rk3399: move CONFIG_SPI and CONFIG_SPI_FLASH to defconfig

On the RK3399-Q7 we need to enable a number of configuration options
(e.g. CONFIG_SPI_FLASH_WINBND) dependent on Kconfig seeing CONFIG_SPI
and CONFIG_SPI_FLASH active.

To allow for these being defined in Kconfig (e.g. via defconfig) and
to avoid a warning on having the macro defined multiple times, we
remove them from the common header file.

Note that the rk3399-evb does not currently have the rk_spi.c driver
active (i.e. CONFIG_ROCKCHIP_SPI), so there's no change to the
evb-rk3399_defconfig as part of this change.

X-AffectedPlatforms: RK3399-Q7
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Acked-by: Simon Glass <sjg@chromium.org>