ST DISCO/NUCLEO: no default COMPONENT_SD

[jeromecoutant]

Description

There is no COMPONENT_SD on ST NUCLEO and DISCO boards.
So default pin configuration doesn't have any sense.

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change

[deepikabhavnani]

@jeromecoutant - Pin configs are not very well documented but the values in target overrides are not just for SD card on-board but also for Arduino header compatible pin outs.

[jeromecoutant]

@deepikabhavnani
after #7979 I will then need to add all NUCLEO and DISCO to add :

"target_overrides": {
    "NUCLEO_xxx": {
         "SPI_CS":   "SPI_CS"

:-(

[deepikabhavnani]

@jeromecoutant - Removing first will be a breaking change. Addition should be done before deletion. I am sorry for additional work in all targets, but that would be a cleaner solution :-)

[yossi2le]

@deepikabhavnani
after #7979 I will then need to add all NUCLEO and DISCO to add :

"target_overrides": {
  "NUCLEO_xxx": {
       "SPI_CS":   "SPI_CS"

:-(

@jeromecoutant for now, you can leave the pins in target overrides of SD component as they are today. those has been taken from the sd-driver repository and hopefully should be correct. In the close future we will start a dialoge process with all teams and partener to decide on the exact SPI_ macros in PinNames.h file. I have a feeling after this procedure things may be much more clear.