bcm96345: correct some 6345 specific stuff

bcm96345: correct some 6345 specific stuff

This fixes some problems with the 6345 support and adds a macro for CPU
identification that is easier on the eyes. The first thing it does is to not
initialize MPI on the 6345 as it does not have PCI. The second thing it does is
to use a static value for the CPU frequency of the 6345 chip to provide an
accurate timer.

Signed-off-by: Axel Gembe <ago@bastart.eu.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@11183 3c298f89-4303-0410-b956-a3cf2f4a3e73