sparc: Fix parport build warnings.

If PARPORT_PC_FIFO is not enabled, do not provide the dma lock
macros and lock definition.  Otherwise:

./arch/sparc/include/asm/parport.h:24:24: warning: ‘dma_spin_lock’ defined but not used [-Wunused-variable]
 static DEFINE_SPINLOCK(dma_spin_lock);
                        ^~~~~~~~~~~~~
./include/linux/spinlock_types.h:81:39: note: in definition of macro ‘DEFINE_SPINLOCK’
 #define DEFINE_SPINLOCK(x) spinlock_t x = __SPIN_LOCK_UNLOCKED(x)

Signed-off-by: David S. Miller <davem@davemloft.net>