nfc: pn533: add UART phy driver

This adds the UART phy interface for the pn533 driver.
The pn533 driver can be used through UART interface this way.
It is implemented as a serdev device.

Cc: Johan Hovold <johan@kernel.org>
Cc: Claudiu Beznea <Claudiu.Beznea@microchip.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

NFC: pn533: add I2C phy driver

This adds the I2C phy interface for the pn533 driver.
This way the driver can be used to interact with I2C
connected pn532 devices.

Signed-off-by: Michael Thalmeier <michael.thalmeier@hale.at>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: pn533: Separate physical layer from the core implementation

The driver now has all core stuff isolated in one file, and all
the hardware link specifics in another. Writing a pn533 driver
on top of another hardware link is now just a matter of adding a
new file for that new hardware specifics.

The first user of this separation will be the i2c based pn532
driver that reuses pn533 core implementation on top of an i2c
layer.

Signed-off-by: Michael Thalmeier <michael.thalmeier@hale.at>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>