stm32/spi: remove peripheral generic param.

[Dirbaio]

No description provided.

[honzasp]

Looking at the generated code for SealedRccPeripheral in _generated.rs, I found that we also maintain a global refcount in rcc::REFCOUNT_STOP1; if I understand correctly, this is used to find out whether we can enter low-power state:

    fn enable_and_reset_with_cs(_cs: critical_section::CriticalSection) {
        #[cfg(feature = "low-power")]
        unsafe {
            crate::rcc::REFCOUNT_STOP1 += 1
        };
        ...
    }
    fn disable_with_cs(_cs: critical_section::CriticalSection) {
        ...
        #[cfg(feature = "low-power")]
        unsafe {
            crate::rcc::REFCOUNT_STOP1 -= 1
        };
    }

It seems that the constructor of the SPI peripheral increments REFCOUNT_STOP1, but the destructor doesn't decrement it. Is that OK? If not, perhaps we can extend the ClockEnableBit structure to also increment/decrement the appropriate global refcount?