ARM: 8609/1: V7M: Add support for the Cortex-M7 processor

Cortex-M7 is a new member of the V7M processor family that adds, among
other things, caches over the features available in Cortex-M4.

This patch adds support for recognising the processor at boot time, and
make use of recently introduced cache functions.

Signed-off-by: Jonathan Austin <jonathan.austin@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Joachim Eastwood <manabian@gmail.com>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>