drivers: spi: stm32: Use 'st,stm32h7-spi' compatible input when possible

Instead of using or'ed list of Kconfig options listing the compatible
series with what can be called "stm32h7 variant", use the matching
compatible information.
This will prevent to update the driver next time that a compatible series
is ported into zephyr.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>