target-i386: Move user-mode exception actions out of user-exec.c

The exception_action() function in user-exec.c is just a call to
cpu_loop_exit() for every target CPU except i386.  Since this
function is only called if the target's handle_mmu_fault() hook has
indicated an MMU fault, and that hook is only called from the
handle_cpu_signal() code path, we can simply move the x86-specific
setup into that hook, which allows us to remove the TARGET_I386
ifdef from user-exec.c.

Of the actions that were done by the call to raise_interrupt_err():
 * cpu_svm_check_intercept_param() is a no-op in user mode
 * check_exception() is a no-op since double faults are impossible
   for user-mode
 * assignments to cs->exception_index and env->error_code are no-ops
 * assigning to env->exception_next_eip is unnecessary because it
   is not used unless env->exception_is_int is true
 * cpu_loop_exit_restore() is equivalent to cpu_loop_exit() since
   pc is 0
which leaves just setting env_>exception_is_int as the action that
needs to be added to x86_cpu_handle_mmu_fault().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Riku Voipio <riku.voipio@linaro.org>
Message-id: 1463494687-25947-7-git-send-email-peter.maydell@linaro.org
