powerpc/83xx: refactor mpc8360e quirk for kmeter1

Move the code for this quirk to a dedicated function.

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>
Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>