i2c: bcm2835: Fix the error handling in 'bcm2835_i2c_probe()'

Some resource should be released if an error occurs in
'bcm2835_i2c_probe()'.
Add an error handling path and the needed 'clk_disable_unprepare()' and
'clk_rate_exclusive_put()' calls.

While at it, rework the bottom of the function to use this newly added
error handling path and have an explicit and more standard "return 0;" at
the end of the normal path.

Fixes: bebff81f ("i2c: bcm2835: Model Divider in CCF")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
[wsa: rebased]
Signed-off-by: Wolfram Sang <wsa@kernel.org>