hub75: fix data buffering

[ehime-iyokan]

I fixed buffering of red data. ( #691 (comment) )

The red data seems to be misaligned, so the display position is incorrect;
however, the other colors are fine.

// Sample code for order of operations
package main

import "fmt"

func main() {
	bitSelect := 2
	data_1 := 0x05
	data_2 := 0x05

	fmt.Println("before")
	fmt.Printf("%08b\n", data_1)
	data_1 = data_1 &^ 1 << bitSelect
	fmt.Printf("%08b\n", data_1)

	fmt.Println("after")
	fmt.Printf("%08b\n", data_2)
	data_2 &^= 1 << bitSelect
	fmt.Printf("%08b\n", data_2)
}

// before: it setting bits to 1 in unintended positions.
// after: it is clearing the bits in the intended positions.
$ go run .    
before
00000101
00010000
after
00000101
00000001

[ehime-iyokan]

I have confirmed sample-program works without any problems. ehime-iyokan/DisplayWeatherInfoOnLEDmatrix@4ec0054