mfd: twl4030-irq: Fix incorrect type in assignment warning

Silences Sparse warning:

 drivers/mfd/twl4030-irq.c:485:26: warning: incorrect type in assignment (different base types)
 drivers/mfd/twl4030-irq.c:485:26:    expected unsigned int [usertype] word
 drivers/mfd/twl4030-irq.c:485:26:    got restricted __le32 [usertype]

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>