target/arm: Fix BTI versus CF_PCREL

target/arm: Fix BTI versus CF_PCREL

With pcrel, we cannot check the guarded page bit at translation
time, as different mappings of the same physical page may or may
not have the GP bit set.

Instead, add a couple of helpers to check the page at runtime,
after all other filters that might obviate the need for the check.

The set_btype_for_br call must be moved after the gen_a64_set_pc
call to ensure the current pc can still be computed.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240802003028.795476-1-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>