mfd: Add Toshiba's TC35892 MFD core

The TC35892 I/O Expander provides 24 GPIOs, a keypad controller, timers,
and a rotator wheel interface.  This patch adds the MFD core.

Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>