target-microblaze: dec_store: Use bool instead of unsigned int

target-microblaze: dec_store: Use bool instead of unsigned int

Use bool instead of unsigned int to represent flags.
Also, use extract32 instead of open coding the bit extract.

No functional change.

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