[PATCH v4 1/2] wire: export w1_touch_bit

[Jan Kandziora]

Changes in v4 against v3 in this subpatch:
  - adapted to linux-4.12.0

No changes in v3 against v2,v1 in this subpatch.

The w1_ds28e17 driver from the next part of this patch needs to emit
single-bit read timeslots to the DS28E17. The w1 subsystem already
has this function but it is not exported outside drivers/w1/w1_io.c

This subpatch exports the w1_touch_bit symbol with EXPORT_SYMBOL_GPL,
same as the other exported symbols in drivers/w1/w1_io.c

May be also useful later for writing drivers for other Onewire chips
which do single-bit communication.


Signed-off-by: Jan Kandziora <jjj@xxxxxx>
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