target/ppc: Fix TCG temporary leaks in gen_slbia()

target/ppc: Fix TCG temporary leaks in gen_slbia()

This fixes:

  $ qemu-system-ppc64 \
  -machine pseries-4.1 -cpu power9 \
  -smp 4 -m 12G -accel tcg ...
  ...
  Quiescing Open Firmware ...
  Booting Linux via __start() @ 0x0000000002000000 ...
  Opcode 1f 12 0f 00 (7ce003e4) leaked temporaries
  Opcode 1f 12 0f 00 (7ce003e4) leaked temporaries
  Opcode 1f 12 0f 00 (7ce003e4) leaked temporaries

[*] https://www.mail-archive.com/qemu-discuss@nongnu.org/msg05400.html

Fixes: 0418bf78fe8 ("Fix ISA v3.0 (POWER9) slbia implementation")
Reported-by: Dennis Clarke <dclarke@blastwave.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-id: 20200417090749.14310-1-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>