A few PMU-related macros are now looking a little lonely in
asm/perf_event.h now that all other PMU-specific structs, function
prototypes and macros live in pmu.h.

So as to make their placement consistent and to make it easier to build
atop of the current PMU functionality, let's reunite the entire family in
pmu.h
Acked-by: NWill Deacon <will.deacon@arm.com>
Tested-by: NChristopher Covington <cov@codeaurora.org>
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>