st/va: flush the context before calling flush_frontbuffer(v2)
st/va: flush the context before calling flush_frontbuffer(v2)

so that the texture is rendered to back buffer before calling
flush_frontbuffer and can be copied to a different buffer in
the function

v2: change comment style

Signed-off-by: Nayan Deshmukh <df308fb4a67a5efb3258393111da6e14db0cf127@gmail.com>
Reviewed-by: Michel Dänzer <242b79f0804cf52679d58f27ed754158c1323c75@amd.com>
Acked-by: Christian König <c7ea837d7a46effe4232b086213468b8b31643bf@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler