ARM: shmobile: BOCK-W: change Ether device name

When changing the name of Ether platform device in the commit c02f8469 (ARM:
shmobile: r8a7778: fix Ether device name), I completely forgot that there's also
platform  device name used in bockw_pinctrl_map[], so the commit "ARM: shmobile:
BOCK-W: add Ether support" went in with the old "sh-eth" device name. Now change
it to "r8a777x-ether" in accordance with the commits that are now in  the  'net-
next.git' repository,  otherwise BOCK-W Ether support won't work in 3.11.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>