platform/x86: topstar-laptop: split ACPI events and input handling

* get the `acpi_device` from the `topstar_laptop` struct,

* split input registering and `sparse_keymap` events from ACPI events
handling,

* use notify, init and exit functions for ACPI and input handling

Signed-off-by: Guillaume Douézan-Grard <gdouezangrard@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>