KVM: arm64: Correct spelling of DBGDIDR register

The aarch32 debug ID register is called DBG*D*IDR (emphasis added), not
DBGIDR, use the correct spelling.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210128132823.35067-1-alexandru.elisei@arm.com