ARM: l2c: move type string into l2c_init_data structure

Rather than decoding this from the ID register, store it in the
l2c_init_data structure.  This simplifies things some more, and
allows us to better provide further details as to how we're
driving the cache.  We print the cache ID value anyway should we
need to precisely identify the cache hardware.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>