ANDROID: sched/debug: Add energy procfs interface

This patch makes the energy data available via procfs. The related files
are placed as sub-directory named 'energy' inside the
/proc/sys/kernel/sched_domain/cpuX/domainY/groupZ directory for those
cpu/domain/group tuples which have energy information.

The following example depicts the contents of
/proc/sys/kernel/sched_domain/cpu0/domain0/group[01] for a system which
has energy information attached to domain level 0.

/--cpu0
|  /--domain0
|  |  /--busy_factor
|  |  |--busy_idx
|  |  |--cache_nice_tries
|  |  |--flags
|  |  |--forkexec_idx
|  |  |--group0
|  |  |  /--energy
|  |  |  |  /--cap_states
|  |  |  |  |--idle_states
|  |  |  |  |--nr_cap_states
|  |  |  |  |--nr_idle_states
|  |  |--group1
|  |  |  /--energy
|  |  |  |  /--cap_states
|  |  |  |  |--idle_states
|  |  |  |  |--nr_cap_states
|  |  |  |  |--nr_idle_states
|  |  |--idle_idx
|  |  |--imbalance_pct
|  |  |--max_interval
|  |  |--max_newidle_lb_cost
|  |  |--min_interval
|  |  |--name
|  |  |--newidle_idx
|  |  |--wake_idx
|  |--domain1
|  |  /--busy_factor
|  |  |--busy_idx
|  |  |--cache_nice_tries
|  |  |--flags
|  |  |--forkexec_idx
|  |  |--idle_idx
|  |  |--imbalance_pct
|  |  |--max_interval
|  |  |--max_newidle_lb_cost
|  |  |--min_interval
|  |  |--name
|  |  |--newidle_idx
|  |  |--wake_idx

The files 'nr_idle_states' and 'nr_cap_states' contain a scalar value
whereas 'idle_states' and 'cap_states' contain a vector of power
consumption at this idle state respectively (compute capacity, power
consumption) at this capacity state.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Change-Id: I2b96d1d46e38d1131e78c206cc1d94900e6d0690
Signed-off-by: Chris Redpath <chris.redpath@arm.com>