package/opencv3: disable VFPv3 options

package/opencv3: disable VFPv3 options

Commit a17402e42d8c996af239cfdb536e74188d6c6245 has conditionally
enabled NEON and VFPv3 optimizations. However, the VFPv3 logic is
causing issues on some targets such as Cortex-A5 with VFPv4-D16 but
not VFPv4.

Since the ENABLE_VFPV3=ON option only adds CFLAGS, we can always set
it to OFF, and let Buildroot pass appropriate CFLAGS.

However, the ENABLE_NEON option also adds the build of NEON-specific
code, so we keep this logic.

Fixes:
 - https://bugs.buildroot.org/show_bug.cgi?id=11996

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>