External dma

[zhenhaohe]

• update packet size to 4K
• host flag fix in firmware
• remove the bo from base buffer and use base buffer as the base class for simbuffer, fpga buffer and coyote buffer
• add the coyote device as seperate hpp and cpp file
• modified the cmake to include the coyote header and sources
• both the coyote host example and xrt host example pass build
• TODO: refactorize the structure of the driver path, probably change the folder of driver/xrt to driver/host