w1: export w1_read_8 function

Export the w1_read_8 function for use of drivers.  The OMAP HDQ
driver(drivers/w1/masters/omap_hdq.c) uses this function.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Madhusudhan <Chikkature&lt;madhu.cr@ti.com>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>