MIPS: Include linux/initrd.h for free_initrd_mem()
arch/mips/mm/init.c provides our implementation of free_initrd_mem(),
but doesn't include the linux/initrd.h header which declares them. This
leads to a warning from sparse:
arch/mips/mm/init.c:501:6: warning: symbol 'free_initrd_mem' was not
declared. Should it be static?
Fix this by including linux/initrd.h to get the declaration of
free_initrd_mem().