ar71xx: ar934x_nfc: fix memory initialization bug

sizeof(array_from_function_definition) gives back the size of the pointer.
sizeof(type)  * array_size   should be used in memset.

Signed-off-by: David Völgyes <david.volgyes@gmail.com>
Patchwork: http://patchwork.openwrt.org/patch/4950/


Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 39890