target/arm: Implement arm_cpu_record_sigsegv

target/arm: Implement arm_cpu_record_sigsegv

Because of the complexity of setting ESR, continue to use
arm_deliver_fault.  This means we cannot remove the code
within cpu_loop that decodes EXCP_DATA_ABORT and
EXCP_PREFETCH_ABORT.

But using the new hook means that we don't have to do the
page_get_flags check manually, and we'll be able to restrict
the tlb_fill hook to sysemu later.

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