dell-wmi: Generate one sparse keymap for all machines

This patch reworks code for generating sparse keymap and processing WMI
events. It unifies procedure for generating sparse keymap and also unifies
big switch code for processing WMI events of different types. After this
patch dell-wmi driver does not differ between "old" and "new" hotkey type.

It constructs sparse keymap table with all WMI codes. It is because on some
laptops (e.g. Dell Latitude E6440) ACPI/firmware send both event types (old
and new).

Each WMI code in sparse keymap table is prefixed by 16bit event type, so it
does not change functionality on laptops with "old" hotkey support (those
without scancodes in DMI).

This allow us to distinguish between same WMI codes with different types in
sparse keymap. Thanks to this WMI events of type 0x0011 were moved from big
switch into sparse keymap table too.

This patch also fixes possible bug in parsing WMI event buffer introduced
in commit 5ea25597 ("dell-wmi: Add support for new Dell systems"). That
commit changed buffer type from int* to u16* without fixing code. More at:
http://lkml.iu.edu/hypermail/linux/kernel/1507.0/01950.html



Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Tested-by: Michał Kępień <kernel@kempniu.pl>
Reviewed-by: Michał Kępień <kernel@kempniu.pl>
Tested-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>