ssb: recognize ARM Cortex M3

I found this core on a BCM4322, a PCI card in the Linksys WRT610N V1.
This core is not used by the driver, this patch just makes ssb show the
correct name.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>