[crc] add crc width enum
[crc] refactoring
fix CRC32 init
add CRC32B init (commonly known as CRC32 -_-)
update crc_update to accept a buffer/len
[crc] crc32b example
pushed by mistake sry
[crc] name not necessary
rtc: Add register definitions
MK20DZ10.h: Remove conflicting RTC definitions
rtc: Add some utility functions