target/microblaze: Tidy do_rti, do_rtb, do_rte

Since cpu_msr is no longer a 64-bit quantity, we can simplify
the arithmetic in these functions.

Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed