sh_eth: get rid of bb_{set|clr|read}()

After the MDIO bitbang code consolidation, there's no need anymore for
bb_{set|clr}() as well as bb_read() -- just expand them inline, thus
saving more LoCs...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>