freedreno/ir3: fix UMAD
freedreno/ir3: fix UMAD

Looks like none of the mad variants do u16 * u16 + u32, so just add in
the extra value "by hand".

Signed-off-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>
Cc: "10.3 10.4" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler