drm/xe/hwmon: Add infra to support card power and energy attributes

drm/xe/hwmon: Add infra to support card power and energy attributes

Add infra to support card power and energy attributes through channel 0.
Package attributes will be now exposed through channel 1 rather than
channel 0 as shown below.

Channel 0 i.e power1/energy1_xxx used for card and
channel 1 i.e power2/energy2_xxx used for package power,energy attributes.

power1/curr1_crit and in0_input are moved to channel 1, i.e.
power2/curr2_crit and in1_input as these are available for package only.

This would be needed for future platforms where they might be
separate registers for package and card power and energy.

Each discrete GPU supported by Xe driver, would have a directory in
/sys/class/hwmon/ with multiple channels under it.
Each channel would have attributes for power, energy etc.

Ex: /sys/class/hwmon/hwmon2/power1_max
                           /power1_label
                           /energy1_input
                           /energy1_label

Attributes will have a label to get more description of it.
Labelling is as below.
		power1_label/energy1_label - "card",
		power2_label/energy2_label - "pkg".

v2: Fix checkpatch errors.

v3:
 - Update intel-xe-hwmon documentation. (Riana, Badal)
 - Rename hwmon card channel enum from CHANNEL_PLATFORM
   to CHANNEL_CARD. (Riana)

v4:
 - Remove unrelated changes from patch. (Anshuman)
 - Fix typo in commit msg.

v5:
 - Update commit message and intel-xe-hwmon documentation with "Xe"
   instead of xe when using it as a name. (Rodrigo)

Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240328175435.3870957-1-karthik.poosa@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>