mfd: ab8500-core MFD devices marked as initdata

Internal MFD device structs are marked as __devinitdata since the kernel
will allocate memory for the same when calling mfd_add_devices.

Signed-off-by: Robert Rosengren <robert.rosengren@stericsson.com>
Reviewed-by: Mattias Wallin <mattias.wallin@stericsson.com>
Reviewed-by: Johan Palsson <johan.palsson@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>