Fix ChibiOS FPU detection.

Fix ChibiOS FPU detection.

This is needed for Cortex-M7 devices, which have newer FPU.
This issue caused the registry integrity check to fail if FPU was enabled.
Currently the code must use FPUv4_SP anyway, since other configurations are not
supported by ChibiOS.

Change-Id: Ie8a2cb8282ccff6c2a3eb0ffeaddaf149d55d685
Signed-off-by: Luca Dariz <luca.dariz@gmail.com>
Reviewed-on: http://openocd.zylin.com/4398
Tested-by: jenkins
Reviewed-by: Karl Palsson <karlp@tweak.net.au>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>