ARM: 8606/1: V7M: introduce cache operations

This commit implements the cache operation for V7M.

It is based on V7 counterpart and differs as follows:
- cache operations are memory mapped
- only Thumb instruction set is supported
- we don't handle user access faults

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>