HID: google: fix unused variable warning under !CONFIG_ACPI

As reported by the kernel test robot, the following warning occurs:

>> drivers/hid/hid-google-hammer.c:261:36: warning: 'cbas_ec_acpi_ids' defined but not used [-Wunused-const-variable=]
     261 | static const struct acpi_device_id cbas_ec_acpi_ids[] = {
         |                                    ^~~~~~~~~~~~~~~~

The 'cbas_ec_acpi_ids' array is only used when CONFIG_ACPI is enabled.
Wrapping its definition and 'MODULE_DEVICE_TABLE' in '#ifdef CONFIG_ACPI'
prevents a compiler warning when ACPI is disabled.

Fixes: eb1aac4c ("HID: google: add support tablet mode switch for Whiskers")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501201141.jctFH5eB-lkp@intel.com/


Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>