arch/mips/mm/cache.c provides our implementation of the cpu_cache_init()
function, but doesn't include the asm/setup.h header which declares it.
This leads to a warning from sparse:
arch/mips/mm/cache.c:274:6: warning: symbol 'cpu_cache_init' was not
declared. Should it be static?
Fix this by including asm/setup.h to get the declaration of
cpu_cache_init().