bbc_i2c: fix section mismatch warning

Fix following warning:

WARNING: drivers/sbus/char/bbc.o(.text+0x674): Section mismatch in reference from the function bbc_i2c_probe() to the function .init.text:T.463()
The function bbc_i2c_probe() references the function __init T.463().
This is often because bbc_i2c_probe lacks a __init
annotation or the annotation of T.463 is wrong.

bbc_i2c_probe() referenced the inlined attach_one_i2c().
As probe may be called after init drop __init annotations
on all functions used by bbc_i2c_probe()

The warning was seen with a sparc64 defconfig build

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>