Fix FDCAN FIFO acknowledge register definition to make it correct for H7
MCUs. Previous definition contained hardcoded offset instead of using
MCU-specific macro.
Fix incorrect decoding of buffer element size. During decoding, value
returned was erratically set to 7 instead of setting 4th LSB. Buffer
element size was then always reported as 15 bytes.
Added some descriptions for missing parameters, (hopefully) clarified
some along the way. Fixed all can related warnings in doxygen logs.
Added doxgen tags where meaningful comments had been provided. Dropped
redundant comment separators.
Add stm32h7 support for FDCAN peripheral. Source level compatibility is
provided with stm32g4. Additional features of stm32h7 such as
configurable buffers are supported. Implementation offers feature parity
with stm32g4 implementation.
