Cortex-M7 handling.

Cortex-M7 handling.

- FPU detection and FPU register support added for Cortex-M7.
  There is no apparent difference between FPv4 and FPv5_SP but ...

- Autoincrement range for MEM-AP added for Cortex-M7

This patch together with #3526 replaces #3123 except for stm32f7x.cfg.

Change-Id: I5ed5392e3835674160563ff37d67622a7bf2c877
Signed-off-by: Andreas Bolsch <hyphen0break@gmail.com>
Reviewed-on: http://openocd.zylin.com/3531
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>