mfd: smsc-ece1099: Remove driver

This MFD driver has no user. The keypad driver of this device never made
it into the kernel. Therefore, this driver is useless. Remove it.

Signed-off-by: Michael Walle <michael@walle.cc>
Cc: Sourav Poddar <sourav.poddar@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>