reset: add driver for socfpga

Add a reset-controller driver for the socfpga platform.
The reset-controller has four banks with up to 32 entries all encapsulated in
one module block.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
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Notes:
    Changes since v2:
        - remove superfluous ret in probe function
        - add Acked-by

    Changes since v1:
        - use BITS_PER_LONG everywhere instead of MAX_BANK_WIDTH
        - print pdev->dev.of_node->full_name on error
        - use proper IS_ERR/PTR_ERR