net: mvneta: Add GPIO configuration support

This patch add GPIO configuration support in mvneta driver.
Driver will handle PHY reset. GPIO pins should be set in device tree.

Ported from mvpp2x
[https://patchwork.ozlabs.org/patch/799654/]

Initial discussion to port the changes into mvneta
[https://patchwork.ozlabs.org/patch/1005765/

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Signed-off-by: Aditya Prayoga <aditya@kobol.io>
Tested-by: Dennis Gilmore <dgilmore@redhat.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>