tgsi: Ensure struct tgsi_ind_register field Index is initialized.

Fixes uninitialized scalar variable defect reported by Coverity.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/gallium/auxiliary/tgsi/tgsi_build.c

@@ -835,6 +835,7 @@ tgsi_default_ind_register( void )
    struct tgsi_ind_register ind_register;
 
    ind_register.File = TGSI_FILE_NULL;
+   ind_register.Index = 0;
    ind_register.Swizzle = TGSI_SWIZZLE_X;
    ind_register.ArrayID = 0;