PPC: Add description for the Freescale e500mc core.

PPC: Add description for the Freescale e500mc core.

This core is found on chips such as p4080, p3041, p2040, and p5020.

More needs to be done to make this viable for TCG (such as missing SPRs
and instructions), but this suffices to get KVM running with appropriate
kernel support.

Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
[scottwood@freescale.com: tweak some flags]
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>