hp-wmi: allow setting input and output buffer sizes separately

Split buffersize parameter of hp_wmi_perform_query to insize and
outsize. Existing callers are changed to use the same value for insize
and outsize to avoid any regressions, with the exception of
hp_wmi_set_block where the output buffer is unused and therefore outsize
is set to 0 (this change is not seen by BIOS code).

The maximum input buffer size is kept at 4 bytes as per struct
bios_args. Some commands exist that take longer buffers, but they
haven't been implemented. The data portion of bios_args can be trivially
made dynamically allocated later when such larger buffers become needed.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Matthew Garrett <mjg@redhat.com>