arm64: proton-pack: Fix hard lockup when !MITIGATE_SPECTRE_BRANCH_HISTORY

arm64: proton-pack: Fix hard lockup when !MITIGATE_SPECTRE_BRANCH_HISTORY

The "drop print" commit removed the whole branch and not just the print.
For some ARM64 cpus, this leads to hard lockup when
CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY is not enabled.

Fixes: 62e72463ca71 ("arm64: proton-pack: Drop print when !CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Will Deacon <will@kernel.org>