Apply CLOCK_BUFFER_TYPE on an input clock to describe
what type of clock buffer to use.
By default, Vivado synthesis uses BUFGs for clock
buffers. Supported values are "BUFG", "BUFH",
"BUFIO", "BUFMR", "BUFR" or
"none". The CLOCK_BUFFER_TYPE attribute can be
placed on any top-level clock port. It can be set in the RTL and XDC.