spi: stm32: deduplicate code creating SPI instances
spi: stm32: deduplicate code creating SPI instances

Create new instances of SPI using single STM32_SPI_INIT() macro
invocation, similar as it is done for STM32 UART driver. Add also
implicit '#ifdef CONFIG_SPI_id' check, so it further reduces required
lines of code for each SPI instance definition.

Signed-off-by: Marcin Niestroj <63506c06cfbc47ace147db1702f6e751f5ac2132@grinn-global.com>

galak/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr