net: marvell: prestera: Add PCI interface support

Add PCI interface driver for Prestera Switch ASICs family devices, which
provides:

    - Firmware loading mechanism
    - Requests & events handling to/from the firmware
    - Access to the firmware on the bus level

The firmware has to be loaded each time the device is reset. The driver
is loading it from:

    /lib/firmware/mrvl/prestera/mvsw_prestera_fw-v{MAJOR}.{MINOR}.img

The full firmware image version is located within the internal header
and consists of 3 numbers - MAJOR.MINOR.PATCH. Additionally, driver has
hard-coded minimum supported firmware version which it can work with:

    MAJOR - reflects the support on ABI level between driver and loaded
            firmware, this number should be the same for driver and loaded
            firmware.

    MINOR - this is the minimum supported version between driver and the
            firmware.

    PATCH - indicates only fixes, firmware ABI is not changed.

Firmware image file name contains only MAJOR and MINOR numbers to make
driver be compatible with any PATCH version.

Co-developed-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>