arm64: perf: Remove duplicate generic cache events

We cannot distinguish reads from writes in our generic cache events, so
drop the WRITE entries and leave the READ entries pointing to the combined
read/write events, as is done by other CPUs and architectures.

Reported-by: Ganapatrao Kulkarni <Ganapatrao.Kulkarni@cavium.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>