NFC: st21nfca: Fix potential memory leak

If all bits of 'dev_mask' are already set, there is a memory leak because
'info' should be freed before returning.

While fixing it, 'return -ENOMEM' directly if the first kzalloc fails.
This makes the code more readable.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>