riscv: dts: microchip: fix fabric i2c reg size

The size of the reg should've been changed when the address was changed,
but obviously I forgot to do so.

Fixes: ab291621

 ("riscv: dts: microchip: icicle: re-jig fabric peripheral addresses")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>