clk: shmobile: check for failure

We were not checking the return from devm_add_action() which can fail.
Start using the helper devm_add_action_or_reset() and return directly
as we know that the cleanup has been done by this helper.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>