[PARISC] Fix uniprocessor build by dummying smp_send_all_nop()

Since irq.c uses smp_send_all_nop, we must define it for UP builds
as well. Make it a static inline so it gets optimized away. This forces
irq.c to include <asm/smp.h> though.

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

arch/parisc/kernel/irq.c

@@ -31,6 +31,8 @@
 #include <linux/spinlock.h>
 #include <linux/types.h>
 
+#include <asm/smp.h>
+
 #undef PARISC_IRQ_CR16_COUNTS
 
 extern irqreturn_t timer_interrupt(int, void *, struct pt_regs *);