Microchip: MEC172x: Device tree constant property cleanup

Microchip XEC two custom DT properies girqs and pcrs cell sizes
are defined as constants. There is no need to replicate these
is the chip DTSI since the value cannot be changes. Fix the syntax
of the cell size constant to match the naming convention used
thoughout DT.

Signed-off-by: Scott Worley <scott.worley@microchip.com>