Now that the 32-bit and 64-bit perf backends use the common groups
directly, remove the fallback and no longer allow the groups array to be
overridden.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>