NFC: s3fwrn5: Remove superfluous cflags

NFC_DEBUG is not defined in Kconfig and since DEBUG is not used
anywhere in this directory, we can safely remove this line.

Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
Acked-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>