kernel/arc: Fix function name collision
kernel/arc: Fix function name collision

Local function os_arch_start() has same name as API function
but different prototype.

Now name is changed so there is no prototype collision.

This does not change any functionality.

mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core