x86/resctrl: Add per-rmid arch private storage for overflow and chunks

A renamed __rmid_read() is intended as the function that an
architecture agnostic resctrl filesystem driver can use to
read a value in bytes from a counter. Currently the function returns
the MBM values in chunks directly from hardware. For bandwidth
counters the resctrl filesystem uses this to calculate the number of
bytes ever seen.

MPAM's scaling of counters can be changed at runtime, reducing the
resolution but increasing the range. When this is changed the prev_msr
values need to be converted by the architecture code.

Add an array for per-rmid private storage. The prev_msr and chunks
values will move here to allow resctrl_arch_rmid_read() to always
return the number of bytes read by this counter without assistance
from the filesystem. The values are moved in later patches when
the overflow and correction calls are moved into __rmid_read().

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jamie Iles <quic_jiles@quicinc.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20220902154829.30399-14-james.morse@arm.com