nand: vybrid: Use calloc() instead of malloc() to allocate struct nfc

nand: vybrid: Use calloc() instead of malloc() to allocate struct nfc

Without this change it is possible that Vybrid's NFC driver malloc() call
will obtain some memory used (and correctly free'd) by some previous
driver (in this case pinctrl for Vybrid).

As a result some fields of struct nfc - in out case mtd->_get_device - are
"pre initialized" with some random values.

On the latter stage of booting, when e.g. somebody calls 'mtdparts default'
the "data abort" is observed when __get_mtd_device() function is called.

The mtd->_get_device pointer is not NULL and wrong value is referenced.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Stefan Agner <stefan.agner@toradex.com>