There are two error return paths that do not kfree clk_data and
we end up with a memory leak. Fix these with a kfree error exit
path.

Detected by CoverityScan, CID#1402959 ("Resource Leak")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>