w1_bq27000 - remove w1_bq27000_write

The function is never used so remove it to avoid bit-rot.
It can trivially be re-added if there is ever a need.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>