target/microblaze: Plug temp leaks for loads/stores

target/microblaze: Plug temp leaks for loads/stores

Simplify endian reversion of address also plugging TCG temp
leaks for loads/stores.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Luc Michel <luc.michel@greensocs.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>