target/arm: Split arm_pre_translate_insn

target/arm: Split arm_pre_translate_insn

Create arm_check_ss_active and arm_check_kernelpage.

Reverse the order of the tests.  While it doesn't matter in practice,
because only user-only has a kernel page and user-only never sets
ss_active, ss_active has priority over execution exceptions and it
is best to keep them in the proper order.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>