tcg/tci: Emit setcond before brcond

The encoding planned for tci does not have enough room for
brcond2, with 4 registers and a condition as input as well
as the label.  Resolve the condition into TCG_REG_TMP, and
relax brcond to one register plus a label, considering the
condition to always be reg != 0.

Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>