target/arm: Convert Extract instructions to decodetree

target/arm: Convert Extract instructions to decodetree

Convert the EXTR instruction to decodetree (this is the
only one in the 'Extract" class). This is the last of
the dp-immediate insns in the legacy decoder, so we
can now remove disas_data_proc_imm().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230512144106.3608981-13-peter.maydell@linaro.org