drivers/net/ethernet/sfc: use standard __{clear,set}_bit_le() functions

There are now standard functions for dealing with little-endian bit
arrays, so use them instead of our own implementations.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>