tools/kwboot: Add parameters to set delay and timeout via cmdline

To support the Armada 38x, new values for the request-delay and the
response-timeout are needed. As the values already implemented in
this tool (for Kirkwood and Armada XP) don't seem to work here.
To make this more flexible, lets add make those 2 parameters
configurable via the cmdline. Here the new parameters:

-q <req-delay>:  use specific request-delay
-s <resp-timeo>: use specific response-timeout

For the Marvell DB-88F6820 these values are known to work:

One board:
-q 2 -s 1

2nd board:
-q 5 -s 5

So this seems to be even board specific. But with this patch now
those values can be specified and tested via the cmdline.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Kevin Smith <kevin.smith@elecsyscorp.com>
Cc: Dirk Eibach <dirk.eibach@gdsys.cc>
Cc: Luka Perkov <luka.perkov@sartura.hr>