The PBL image tool includes two commands into the image. These are executed
after the initial image has been uploaded but before the final CRC
check. These commands are "flush" and "wait". According to the reference
manual a "flush" command can be used to read back the the value just
written to CCSR register space in order to let the previous write
complete. This seems unnecessary as the last write was never to the CCSR
register space. The "wait" command also seems unnecessary as the time
parameter is 0. As all this end_cmd stuff goes back to the PowerPC times
and everything still seems to work on Arm let's just remove it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>