uapi: fix linux/nfc.h userspace compilation errors

Replace sa_family_t with __kernel_sa_family_t to fix the following
linux/nfc.h userspace compilation errors:

/usr/include/linux/nfc.h:266:2: error: unknown type name 'sa_family_t'
  sa_family_t sa_family;
/usr/include/linux/nfc.h:274:2: error: unknown type name 'sa_family_t'
  sa_family_t sa_family;

Fixes: 23b7869c ("NFC: add the NFC socket raw protocol")
Fixes: d646960f ("NFC: Initial LLCP support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>