powerpc: Fix potential compile error irqs_disabled_flags

irqs_disabled_flags is #defined in linux/irqflags.h when
CONFIG_TRACE_IRQFLAGS_SUPPORT is enabled.  64 and 32 bit always have
CONFIG_TRACE_IRQFLAGS_SUPPORT enabled so just remove
irqs_disabled_flags.

This fixes the case when someone needs to include both linux/irqflags.h
and asm/hw_irq.h.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/hw_irq.h

@@ -64,11 +64,6 @@ extern void iseries_handle_interrupts(void);
 		get_paca()->hard_enabled = 0;	\
 	} while(0)
 
-static inline int irqs_disabled_flags(unsigned long flags)
-{
-	return flags == 0;
-}
-
 #else
 
 #if defined(CONFIG_BOOKE)