spi: stm32: rename stm32f4_* to stm32fx_*

The STM32F4 and STM32F7 SPI peripherals are very similar, therefore
most of the driver can be shared between the two. In preparation for
adding support for the F7, change all functions and defines to use a
generic stm32fx prefix, except for code and registers that differ
between the two devices.
Signed-off-by: Ben Wolsieffer <ben.wolsieffer@hefring.com>
Link: https://lore.kernel.org/r/20231102193722.3042245-2-ben.wolsieffer@hefring.comSigned-off-by: Mark Brown <broonie@kernel.org>