net: gmac_rockchip: Add support for the RK3399 GMAC

net: gmac_rockchip: Add support for the RK3399 GMAC

The GMAC in the RK3399 is very similar to the RK3288 variant (i.e. it
is a Designware GMAC core and requires similar configuration as the
RK3288 to switch it to RGMII and set up the TX/RX delays for Gigabit).
The key difference is that the register offsets (within the GRF block)
and bit-offsets (within those registers) used to hold the configuration
differ between the various RK32/33 CPUs.

This change refactors the gmac_rockchip.c driver to use a function
table (selected via driver_data) to factor out these differences. Each
function's implementation then matches the underlying processor.

Some collateral changes are needed in the definitions describing the
bits and offsets in the GRF are needed to prefix each set of symbolic
constants with the SoC name to avoid name clashes... and in doing so,
the shifts for masks and constants have been moved into the header
files for readability (and to make it easier to stay below 80 chars).

X-AffectedPlatforms: RK3399-Q7
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Klaus Goger <klaus.goger@theobroma-systems.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>
Fixed commit message typo s/factor our/factor out/:
Signed-off-by: Simon Glass <sjg@chromium.org>