[ARM] pxa: introduce sysdev for IRQ register saving/restoring

Signed-off-by: eric miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-pxa/generic.h

@@ -52,3 +52,5 @@ extern unsigned pxa3xx_get_memclk_frequency_10khz(void);
 #define pxa3xx_get_clk_frequency_khz(x)		(0)
 #define pxa3xx_get_memclk_frequency_10khz()	(0)
 #endif
+
+extern struct sysdev_class pxa_irq_sysclass;