ARM: kona: fix clk_bsc_enable() type mismatch for LTO

When building with LTO, the compiler complains about type mismatch of
function clk_bsc_enable() in file:
  arch/arm/cpu/armv7/kona-common/clk-stubs.c
vs other files that define or use this function:
  warning: type of ‘clk_bsc_enable’ does not match original declaration.

Change the type of this function to that of the other usages.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>