i2c: atr: Fix end of loop test in i2c_atr_find_mapping_by_addr()

i2c: atr: Fix end of loop test in i2c_atr_find_mapping_by_addr()

When the list_for_each_entry_reverse() exits without hitting a break
then the list cursor points to invalid memory.  So this check for
if (c2a->fixed) is checking bogus memory.  Fix it by using a "found"
variable to track if we found what we were looking for or not.

The list head (i2c_atr_chan.alias_pairs) is not a full entry, it's just
a struct list_head. When the for loop runs to completion, c2a doesn't
point to a struct i2c_atr_alias_pair, so you can't access c2a->fixed.

Fixes: c3f55241882b ("i2c: Support dynamic address translation")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Romain Gantois <romain.gantois@bootlin.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>