[U-Boot] Interrupt issue about bootvx command

[Peter Pan]

Hi Wolfgang,

This is a customized board, which is very similar with Freescale's
P1020RDB (which is p1_p2_rdb in u-boot), only we replace the process
with a compatible one-core version.
And the board support files are mostly copied from the p1_p2_rdb.

And the following is my updated patch. My git does not have "git
send-mail" supported, so I have to paste the formatted commit below.
Sorry for that.