hw/arm/highbank: Drop unused secondary boot stub code

hw/arm/highbank: Drop unused secondary boot stub code

The highbank and midway board code includes boot-stub code for
handling secondary CPU boot which keeps the secondaries in a pen
until the primary writes to a known location with the address they
should jump to.

This code is never used, because the boards enable QEMU's PSCI
emulation, so secondary CPUs are kept powered off until the PSCI call
which turns them on, and then start execution from the address given
by the guest in that PSCI call.  Delete the unreachable code.

(The code was wrong for midway in any case -- on the Cortex-A15 the
GIC CPU interface registers are at a different offset from PERIPHBASE
compared to the Cortex-A9, and the code baked-in the offsets for
highbank's A9.)

Note that this commit implicitly depends on the preceding "Don't
write secondary boot stub if using PSCI" commit -- the default
secondary-boot stub code overlaps with one of the highbank-specific
bootcode rom blobs, so we must suppress the secondary-boot
stub code entirely, not merely replace the highbank-specific
version with the default.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Tested-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20220127154639.2090164-15-peter.maydell@linaro.org