arm: Adjust cortex-m7 support to reflect its ARMv7-M architecture.

The cortex-m7 is an implementation of armv7-m.  Adjust the Kconfig
support for cortex-m7 to reflect this and drop the unnecessary,
explicit, conditional compilation.

Change-Id: I6ec20e69c8c83c5a80b1f714506f7f9e295b15d5
Signed-off-by: Marcus Shawcroft <marcus.shawcroft@arm.com>
16 files changed