NFC: Change nfc.h license

nfc.h being GPL makes it quite controversial for non GPL applications to
include it.
Moreover, nfc.h only includes structures and API definitions that are hardly
copyrightable.

Signed-off-by: Lauro Ramos Venancio <lauro.venancio@openbossa.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>