spi/api: extend with vendor specific configs
spi/api: extend with vendor specific configs

Some drivers would need some specific configuration flags,
re-introduce a vendor specific field for this purpose.

Signed-off-by: Jorge Ramirez-Ortiz <2faea71c6092997fe41b87a2432a9fbfe1779204@linaro.org>
Signed-off-by: Neil Armstrong <619b324efbf5f7848de055bdc8bef4c0dd7c8ef5@baylibre.com>

ldts/zephyr,runchip/zephyr-cc3220,galak/zephyr,holtmann/zephyr,punitvara/zephyr,Vudentz/zephyr,fbsder/zephyr,ldts/zephyr,fbsder/zephyr,punitvara/zephyr,zephyriot/zephyr,nashif/zephyr,kraj/zephyr,zephyriot/zephyr,finikorg/zephyr,zephyriot/zephyr,galak/zephyr,rsalveti/zephyr,fbsder/zephyr,explora26/zephyr,Vudentz/zephyr,aceofall/zephyr-iotos,Vudentz/zephyr,nashif/zephyr,holtmann/zephyr,mbolivar/zephyr,finikorg/zephyr,kraj/zephyr,ldts/zephyr,zephyriot/zephyr,punitvara/zephyr,nashif/zephyr,rsalveti/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,runchip/zephyr-cc3220,rsalveti/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,fbsder/zephyr,rsalveti/zephyr,runchip/zephyr-cc3220,rsalveti/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,fbsder/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,punitvara/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,holtmann/zephyr,aceofall/zephyr-iotos,kraj/zephyr,nashif/zephyr,galak/zephyr,ldts/zephyr,galak/zephyr,runchip/zephyr-cc3220,aceofall/zephyr-iotos,mbolivar/zephyr,mbolivar/zephyr,zephyriot/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,Vudentz/zephyr,finikorg/zephyr,aceofall/zephyr-iotos,explora26/zephyr,kraj/zephyr,holtmann/zephyr,finikorg/zephyr,holtmann/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,runchip/zephyr-cc3220