The jump command is almost identical to the CALL command, with the
difference that CALL command saves stack and allows the called code
to return into the BootROM. JUMP command does not do that, it just
sets the PC register to a value and that's it.

The sematics of both commands are almost identical though, therefore
implement JUMP as a minor adjustment to CALL.

Signed-off-by: Marek Vasut <marex@denx.de>