ANDROID: arm64: Initialise mismatched compat hwcaps from CPU notifier

When CPUs with mismatched support for 32-bit EL0 are detected early,
before the system capabilities are finalised, then initialisation of
the compat hwcaps is left to the boot CPU to configure as it would do
for a system without a mismatch.

Unfortunately, this initialisation is only carried out if
system_supports_32bit_el0(), which isn't initialised until later in the
boot process via a CPU hotplug notifier. Consequently, the compat hwcaps
reported do not necessarily indicate all of the CPU features available.

Move the initialisation of compat hwcaps to the CPU hotplug notifier
itself so that we can ensure that they are configured as soon as we have
detected a mismatch.

Bug: 186482502
Cc: Quentin Perret <qperret@google.com>
Cc: Huang Yiwei <hyiwei@codeaurora.org>
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I54edcc34f96be9dec15aa44407441c0227c17753