target/ppc: Move dtstdc[q]/dtstdg[q] to decodetree

target/ppc: Move dtstdc[q]/dtstdg[q] to decodetree

Move the following instructions to decodetree:
dtstdc:  DFP Test Data Class
dtstdcq: DFP Test Data Class Quad
dtstdg:  DFP Test Data Group
dtstdgq: DFP Test Data Group Quad

Signed-off-by: Luis Pires <luis.pires@eldorado.org.br>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211029192417.400707-10-luis.pires@eldorado.org.br>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>