Input: elan_i2c_core - move header inclusion inside

The same clause as its use.

Fixes the following W=1 kernel build warning(s):

 include/linux/input/elan-i2c-ids.h:26:36: warning: ‘elan_acpi_id’ defined but not used [-Wunused-const-variable=]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201112104420.GG1997862@dell


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>