arm: fix qemu crash on startup with -bios option

arm: fix qemu crash on startup with -bios option

When QEMU is started with following CLI
 -machine virt,gic-version=3,accel=kvm -cpu host -bios AAVMF_CODE.fd
it crashes with abort at
 accel/kvm/kvm-all.c:2164:
 KVM_SET_DEVICE_ATTR failed: Group 6 attr 0x000000000000c665: Invalid argument

Which is caused by implicit dependency of kvm_arm_gicv3_reset() on
arm_gicv3_icc_reset() where the later is called by CPU reset
reset callback.

However commit:
 3b77f6c arm/boot: split load_dtb() from arm_load_kernel()
broke CPU reset callback registration in case

  arm_load_kernel()
      ...
      if (!info->kernel_filename || info->firmware_loaded)

branch is taken, i.e. it's sufficient to provide a firmware
or do not provide kernel on CLI to skip cpu reset callback
registration, where before offending commit the callback
has been registered unconditionally.

Fix it by registering the callback right at the beginning of
arm_load_kernel() unconditionally instead of doing it at the end.

NOTE:
 we probably should eliminate that dependency anyways as well as
 separate arch CPU reset parts from arm_load_kernel() into CPU
 itself, but that refactoring that I probably would have to do
 anyways later for CPU hotplug to work.

Reported-by: Auger Eric <eric.auger@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Message-id: 1527070950-208350-1-git-send-email-imammedo@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>