arm64: don't select PERF_USE_VMALLOC by default

Any arm64 based parts that have cache aliasing issues can set it
manually.  Apparently dragged in from ARM(32) defaults in commit
8c2c3df3 "arm64: Build infrastructure".

Signed-off-by: Kim Phillips <kim.phillips@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>