dmaengine: stm32-mdma: Add a check on read_u32_array

In stm32_mdma_probe, after reading the property "st,ahb-addr-masks", the
second call is not checked for failure. This time of check to time of use
case of "count" error is sent upstream.

Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Acked-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>