Don't reset SYSCFG peripherals or switch system clock in embassy_stm32::init

[meowcakes]

If the bootloader uses OSPI to memory map external flash and/or RAM (e.g. if the application binary is too large for embedded flash), calling embassy_stm32::init breaks it due to two reasons (that I am able to tell):

• SYSCFG is reset here

  embassy/embassy-stm32/src/lib.rs

  Line 518 in 06869e2

  rcc::enable_and_reset_with_cs::<peripherals::SYSCFG>(cs);

• The system clock is switched here

  embassy/embassy-stm32/src/rcc/h.rs

  Line 419 in 06869e2

  RCC.cfgr().modify(|w| w.set_sw(Sysclk::HSI));