ARM: perf: assign pdev pointer earlier for CPU PMUs

We want to inspect the of_node that the pdev is pointing to in
the Krait CPU specific PMU initialization function. Assign it
earlier so that we don't crash with a NULL pointer dereference.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>