d3d8: Sign-compare warnings fix

[Andrew Talbot]

Changelog:
    d3d8: Sign-compare warnings fix.

diff --git a/dlls/d3d8/surface.c b/dlls/d3d8/surface.c
index 6ecd7af..a272ed7 100644
--- a/dlls/d3d8/surface.c
+++ b/dlls/d3d8/surface.c
@@ -185,8 +185,8 @@ static HRESULT WINAPI IDirect3DSurface8Impl_LockRect(LPDIRECT3DSURFACE8 iface, D
                 || (pRect->top < 0)
                 || (pRect->left >= pRect->right)
                 || (pRect->top >= pRect->bottom)
-                || (pRect->right > desc.Width)
-                || (pRect->bottom > desc.Height)) {
+                || (pRect->right > (LONG)desc.Width)
+                || (pRect->bottom > (LONG)desc.Height)) {
             WARN("Trying to lock an invalid rectangle, returning D3DERR_INVALIDCALL\n");
             LeaveCriticalSection(&d3d8_cs);
             return D3DERR_INVALIDCALL;