m5core2 uses DC-DC3 to control brightness rather than using LDO2. DC-DC3 is controlled by the 7 least significant bits in the 0x27 register; the most significant bit is reserved. As a result the brightness value shifts left 3 places rather than 4. in order to set the register I read the entire byte, logical AND with 0x80 to clear all bits except the reserved bit, logical OR with the shifted brightness value.
added brightness to the sample m5core2 config
