* in main():
** errx()/err()/return -> exit()
** return values -> EXIT_SUCCESS & EXIT_FAILURE
* out of main:
** err()/errx()/exit() -> return
** change retval from size_t to int to allow returning errors
** don't use EXIT_SUCCESS / EXIT_FAILURE as retvals
* add nfc_close() & nfc_exit() to exit() on errors
* add missing fclose() on errors
* add missing test if (pnd == NULL)
* unify style if (pnd == / != NULL)
* remove goto's
* few related fixes
* remove if(pnd!=NULL) test on nfc_close() calls
- Rename nfc-probe to nfc-scan-device
- Rename internal drivers function prototypes: _probe to _scan
- Revamp _scan function prototype: it now returns device found count
