ARM: shmobile: armadillo: fixup ether pinctrl naming

e5c9b4cd ("sh_eth: get R8A7740 support
out of #ifdef") exchanged sh-eth driver name to r8a7740-gether, but,
eva_pinctrl_map[] didn't follow it. Fixes it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>