lm832x: Take DeviceState pointer in lm832x_key_event()

lm832x: Take DeviceState pointer in lm832x_key_event()

Since lm832x has been qdev'ified, its users will generally
have a DeviceState pointer rather than an i2c_slave pointer,
so adjust lm832x_key_event's prototype to suit.

This allows the n810 (its only user) to actually pass a correct
pointer to it rather than NULL. The effect is that we no longer
segfault when a key is pressed.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>