spi: Drop spi_controller type

Not needed anymore. Drop it fast before it encourages anyone to
violate layers again!

Change-Id: I8eda93b429e3ebaef79e22aba76be62987e496f4
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/33651
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
18 files changed