Make I2C and SPI drivers for nRF SoCs no longer dependent on Kconfig
options that enable instances (i.e. I2C_x and SPI_x). Now these drivers
enable hardware instances when corresponding nodes in devicetree are
enabled (have status "okay").
For I2C, SPI, and UART drivers, instead of using Kconfig dependencies
to prevent enabling of hardware instances that cannot be used together
(e.g. SPIM1 and TWIM1), a file that signals invalid configurations with
build assertions is added to compilation.
Also dependencies on HAS_HW_NRF_* options are removed from Kconfigs
of I2C, SPI, and UART drivers, as for hidden options that activate
proper type of driver such dependencies are not actually helpful.
Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>