arm64: dts: juno: describe PMUs separately

The A57 and A53 PMUs in Juno support different events, so describe them
separately in both the Juno and Juno R1 DTs.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>