sys/dev/cfi: include sys/types.h as well

This will soon be a dependency for machine/atomic.h on mips with the
introduction of 64-bit atomics; the scope here is pretty narrow, so throw it
here in the header just before systm.h, which includes machine/atomic.h

(cherry picked from commit 85ccd84cb3ce35f830cd4c07154152daf41181ef)