hwspinlock: u8500_hsem: Use devm_kzalloc() to allocate memory

Use devm_kzalloc() to allocate memory.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>