Use a 64 bit read to access GICR_TYPER

The GICv3 ITS only needs to implement 32 bit access to the GICR_TYPER
when the CPU implements AArch32. As this may not always be the case
use a 64 bit read when checking if the ITS is enabled on the CPU.

PR: 258217
Reported by: Olivier Delande <olivier.delande@provenrun.com>
Sponsored by: The FreeBSD Foundation