armv7m: Report no-coprocessor faults correctly

For v7M attempts to access a nonexistent coprocessor are reported
differently from plain undefined instructions (as UsageFaults of type
NOCP rather than type UNDEFINSTR).  Split them out into a new
EXCP_NOCP so we can report the FSR value correctly.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1485285380-10565-8-git-send-email-peter.maydell@linaro.org