HID: i2c-hid: Use devm to allocate i2c_hid struct

Use devm here to save some lines and prepare for bulk regulator usage in
this driver. Otherwise, when we devm bulk get regulators we'll free the
containing i2c_hid structure and try to put regulator pointers from
freed memory.

Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Dmitry Torokhov <dtor@chromium.org>
Cc: Doug Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>