mfd: sec-core: Silence compiler warning

When used 64bit compiler GCC warns as
drivers/mfd/sec-core.c:199:10: warning:
cast from pointer to integer of different size [-Wpointer-to-int-cast]

Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>