pvscsi: fix compilation on 32 bit hosts

pvscsi: fix compilation on 32 bit hosts

This fixes the following error:
In file included from qemu/include/trace.h:4:0,
                 from trace/generated-events.c:3:
./trace/generated-tracers.h: In function ‘trace_pvscsi_get_sg_list’:
./trace/generated-tracers.h:4271:9: error: format ‘%lu’ expects argument of
type ‘long unsigned int’, but argument 4 has type ‘size_t’ [-Werror=format]

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>