The ID register table should have one entry per ID register but
currently has two entries for ID_AA64ISAR2_EL1. Only one entry has an
override, and get_arm64_ftr_reg() can end up choosing the other, causing
the override to be ignored. Fix this by removing the duplicate entry.

While here, also make the check in sort_ftr_regs() more strict so that
duplicate entries can't be added in the future.

Fixes: def8c222 ("arm64: Add support of PAuth QARMA3 architected algorithm")
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220511162030.1403386-1-kristina.martsenko@arm.comSigned-off-by: Will Deacon <will@kernel.org>