board/BuR/tseries: remove lpj= from environment-variable

since we have now various processor-speeds it isn't useful anymore to
preinitialize kernels-delay loop.

Rather we want the kernel to calibrate it on every boot.
This wastes around 80ms boottime but is compatible to all CPU-speeds.

Signed-off-by: Hannes Schmelzer <oe5hpm@oevsv.at>