drivers/net/ethernet/dec/tulip: Use standard __set_bit_le() function

To introduce generic set_bit_le() later, we remove our own definition
and use a proper non-atomic bitops function: __set_bit_le().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Acked-by: Grant Grundler <grundler@parisc-linux.org>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>