platform/x86: fujitsu-laptop: explicitly pass ACPI device to call_fext_func()

Prepare for not using module-wide data in call_fext_func() by explicitly
passing it a pointer to struct acpi_device while still using a
module-wide pointer in each call.

Doing this enables call_fext_func() to fetch the ACPI handle from its
argument, making the acpi_handle field of struct fujitsu_laptop useless,
so remove that field.  While we are at it, the dev field of the same
structure is assigned in acpi_fujitsu_laptop_add() but not used for
anything, so remove it as well.

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Reviewed-by: Jonathan Woithe <jwoithe@just42.net>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>