refactor(amu): detect architected counters at runtime

This change removes the `AMU_GROUP0_COUNTERS_MASK` and
`AMU_GROUP0_MAX_COUNTERS` preprocessor definitions, instead retrieving
the number of group 0 counters dynamically through `AMCGCR_EL0.CG0NC`.

Change-Id: I70e39c30fbd5df89b214276fac79cc8758a89f72
Signed-off-by: Chris Kay <chris.kay@arm.com>
5 files changed