powerpc/kconfig: Remove TSI108_BRIDGE duplicates

The MPC7448HPC2 and PPC_HOLLY config options contain TSI108_BRIDGE
duplicates since commit:

commit 3490cba5
Author: Jon Loeliger <jdl@jdl.com>
Date:   Wed Jan 23 12:42:50 2008 -0600

    [POWERPC] Add initial iomega StorCenter board port.

This patch cleans these duplicates.

Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>