ARM: perf: check that we have a platform device when reserving PMU
Attempting to use a hardware counter on a platform with a supported PMU
but where the platform_device (defining the interrupts) has not been
registered results in a NULL pointer dereference.
This patch fixes the problem by checking that we actually have a platform
device registered before attempting to grab the interrupts.
Reported-by: Pawel Moll <pawel.moll@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>