Revert "drivers: spi: stm32h7: Use FIFO"

This reverts commit bffa0c6bddbc91d39f4b01baa34e3d0595760d50.

This FIFO implementation causes a regression by which the SPI
peripheral generates several spurious SCK cyles after the last
data has been sent.

Signed-off-by: Daniel Gaston Ochoa <dgastonochoa@gmail.com>