stm32f205_timer: Split into a header file

Signed-off-by: Alistair Francis <alistair23@gmail.com>
stm32f205: Rename structs to match QEMU style

Also start to build the STM32F205 SoC

Signed-off-by: Alistair Francis <alistair23@gmail.com>
stm32f205: Fix a segfault caused by a NULL cpu type

Signed-off-by: Alistair Francis <alistair23@gmail.com>
stm32f205: Update internal names

Signed-off-by: Alistair Francis <alistair23@gmail.com>
stm32f205: Correctly attach USART

Signed-off-by: Alistair Francis <alistair23@gmail.com>