dt-bindings: pinctrl: aspeed-g6: Rework SD3 function and groups

dt-bindings: pinctrl: aspeed-g6: Rework SD3 function and groups

Rename SD3 functions and groups to EMMC to better reflect their intended
use before the binding escapes too far into the wild. Also clean up the
SD3 pin groups to eliminate some silliness that slipped through the
cracks (SD3DAT[4-7]) by unifying them into three new groups: EMMCG1,
EMMCG4 and EMMCG8 for 1, 4 and 8-bit data buses respectively.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Link: https://lore.kernel.org/r/20191008044153.12734-2-andrew@aj.id.au
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>