virgl: add support for PIPE_TRANSFER_MAP_DIRECTLY

Treat it as mapping the guest storage directly.

This is necessitated by a recent change to st/mesa (commit
ce04fbf6) which assumes PIPE_TRANSFER_MAP_DIRECTLY is always
supported.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
13 jobs for !1400 with virgl-map-directly in 8 minutes and 23 seconds (queued for 4 seconds)
latest detached
Status Job ID Name Coverage
  Containers Build
passed #434538
debian

00:00:19

 
  Build+Test
passed #434547
meson-arm64

00:01:52

passed #434546
meson-armhf

00:01:44

passed #434540
meson-clang

00:06:21

passed #434544
meson-clover

00:08:03

passed #434548
meson-i386

00:01:17

passed #434543
meson-main

00:05:13

passed #434539
meson-swr-glvnd

00:02:31

passed #434545
meson-vulkan

00:01:01

passed #434550
scons-llvm

00:05:36

passed #434549
scons-nollvm

00:02:41

passed #434541
scons-swr

00:05:04

passed #434542
scons-win64

00:06:45