platform/x86: thinkpad_acpi: Select INPUT_SPARSEKMAP in Kconfig

Now that drivers/platform/x86/thinkpad_acpi.c uses
sparse_keymap_report_event(), it must select INPUT_SPARSEKMAP in its
Kconfig option otherwise the build fails with:

  ld: vmlinux.o: in function `tpacpi_input_send_key':
  thinkpad_acpi.c:(.text+0xd4d27f): undefined reference to `sparse_keymap_report_event'
  ld: vmlinux.o: in function `hotkey_init':
  thinkpad_acpi.c:(.init.text+0x66cb6): undefined reference to `sparse_keymap_setup'

Fixes: 42f7b965

 ("platform/x86: thinkpad_acpi: Switch to using sparse-keymap helpers")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20240522074813.379b9fc2@gandalf.local.home
Signed-off-by: Hans de Goede <hdegoede@redhat.com>