ARM: perf: clean and update ARMv7 event numbers

This patch updates the ARMv7 perf event numbers so that:

(1) A consistent naming scheme is used between different CPUs.

(2) Only events actually used by Linux are described.

(3) Where possible, architected events are used in preference to
    CPU-specific events.

This results in the removal of a load of unused, hardcoded data and
makes it more clear as to which events are supported on each PMU.

Cc: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>