fix (spi_oled_example) command bug (GIT8266O-307)

[gengyuchao]

根据SSD1306的手册
设置点坐标高4位时 范围是 0x10-0x1F 需要加入掩码0x10
设置坐标的低4位时 范围为 0x00-0x0F 直接写入

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