platform/x86: panasonic-laptop: de-obfuscate button codes

In the definition of panasonic_keymap[] the key codes are given in
decimal, later checks are done with hexadecimal values, which does
not help in understanding the code.
Additionally use two helper variables to shorten the code and make
the logic more obvious.

Fixes: ed83c917

 ("platform/x86: panasonic-laptop: Resolve hotkey double trigger bug")
Signed-off-by: Stefan Seyfried <seife+kernel@b1-systems.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220624112340.10130-3-hdegoede@redhat.com