platform/x86: ideapad-laptop: Squelch ACPI event 1

Don't simply throw this to userspace via the sparse_keymap (which does not
have a mapping for scancode 1), as this causes KEY_UNKNOWN to be emitted,
which is a nuisance and of no use at all (it is not the right way to expose
this ACPI event to userspace, anyway, and the original intention of the commit
which added this (cfee5d63) was only to suppress
an unhandled event log message).

Signed-off-by: Hao Wei Tee <angelsl@angelsl.xyz>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>