target/arm: do not use cc->do_interrupt for KVM directly

cc->do_interrupt is in theory a TCG callback used in accel/tcg only,
to prepare the emulated architecture to take an interrupt as defined
in the hardware specifications,

but in reality the _do_interrupt style of functions in targets are
also occasionally reused by KVM to prepare the architecture state in a
similar way where userspace code has identified that it needs to
deliver an exception to the guest.

In the case of ARM, that includes:

1) the vcpu thread got a SIGBUS indicating a memory error,
and we need to deliver a Synchronous External Abort to the guest to
let it know about the error.
2) the kernel told us about a debug exception (breakpoint, watchpoint)
but it is not for one of QEMU's own gdbstub breakpoints/watchpoints
so it must be a breakpoint the guest itself has set up, therefore
we need to deliver it to the guest.

So in order to reuse code, the same arm_do_interrupt function is used.
This is all fine, but we need to avoid calling it using the callback
registered in CPUClass, since that one is now TCG-only.

Fortunately this is easily solved by replacing calls to
CPUClass::do_interrupt() with explicit calls to arm_do_interrupt().

Backports 853bfef4e6d60244fd131ec55bbf1e7caa52599b. We don't support
KVM, so we just bring the comment addition over.

qemu/target/arm/helper.c

@@ -9683,6 +9683,10 @@ static inline bool check_for_semihosting(CPUState *cs)
  * Do any appropriate logging, handle PSCI calls, and then hand off
  * to the AArch64-entry or AArch32-entry function depending on the
  * target exception level's register width.
+ *
+ * Note: this is used for both TCG (as the do_interrupt tcg op),
+ *       and KVM to re-inject guest debug exceptions, and to
+ *       inject a Synchronous-External-Abort.
  */
 void arm_cpu_do_interrupt(CPUState *cs)
 {