mfd: Add MODULE_DEVICE_TABLE to mc13xxx-core

The device table is required to load modules based on modaliases.
After adding the MODULE_DEVICE_TABLE, below entries will be added to
modules.alias:
alias spi:mc13892 mc13xxx_core
alias spi:mc13783 mc13xxx_core

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>