mfd: twl4030-irq: Fix cast to restricted __le32 warning

Silences Sparse warning(s):

 drivers/mfd/twl4030-irq.c:573:40: warning: cast to restricted __le32
 drivers/mfd/twl4030-irq.c:573:40: warning: cast to restricted __le32
 drivers/mfd/twl4030-irq.c:573:40: warning: cast to restricted __le32
 drivers/mfd/twl4030-irq.c:573:40: warning: cast to restricted __le32
 drivers/mfd/twl4030-irq.c:573:40: warning: cast to restricted __le32
 drivers/mfd/twl4030-irq.c:573:40: warning: cast to restricted __le32

Cc: Tony Lindgren <tony@atomide.com>
Cc: Kai Svahn <kai.svahn@nokia.com>
Cc: Syed Khasim <x0khasim@ti.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>