Commit 353ac78d moved the files
without fixing the include paths. It used a modified CFLAGS
to add hw to the include search path, but this breaks builds
where the user wants to set special CFLAGS. Long include paths
also increase compilation time.

Therefore this patch removes the special CFLAGS for virtio
and fixes the include statements by using relative include paths.

v2: Remove special CFLAGS.
v3: Update needed for latest QEMU.
Signed-off-by: NStefan Weil <weil@mail.berlios.de>
Signed-off-by: NVenkateswararao Jujjuri (JV) <jvrao@linux.vnet.ibm.com>