powerpc/85xx: sbc8560 - remove "has-rstcr" from global utilities block

The earlier mpc8560 CPUs don't have the RSTCR at 0xe00b0
in the GUTS.  The generic reboot code uses this tag to
determine if it should be using the RSTCR for reboot, so
remove it from the board definition.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>