dmaengine: stm32-mdma: disable clock in case of error during probe

This patch disables the clock in case of error during probe. The unneeded
err_unregister label is renamed err_clk instead.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Link: https://lore.kernel.org/r/20200127085334.13163-4-amelie.delaunay@st.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>