drm/xe/uapi: Introduce API for EU stall sampling

A new hardware feature first introduced in PVC gives capability to
periodically sample EU stall state and record counts for different stall
reasons, on a per IP basis, aggregate across all EUs in a subslice and
record the samples in a buffer in each subslice. Eventually, the aggregated
data is written out to a buffer in the memory. This feature is also
supported in XE2 and later architecture GPUs.

Use an existing IOCTL - DRM_IOCTL_XE_OBSERVATION as the interface into the
driver from the user space to do initial setup and obtain a file descriptor
for the EU stall data stream.  Input parameter to the IOCTL is a struct
drm_xe_observation_param in which observation_type should be set to
DRM_XE_OBSERVATION_TYPE_EU_STALL, observation_op should be
DRM_XE_OBSERVATION_OP_STREAM_OPEN and param should point to a chain of
drm_xe_ext_set_property structures in which each structure has a pair of
property and value. The EU stall sampling input properties are defined in
drm_xe_eu_stall_property_id enum.

With the file descriptor obtained from DRM_IOCTL_XE_OBSERVATION, user space
can enable and disable EU stall sampling with the IOCTLs:
DRM_XE_OBSERVATION_IOCTL_ENABLE and DRM_XE_OBSERVATION_IOCTL_DISABLE.
User space can also call poll() to check for availability of data in the
buffer. The data can be read with read(). Finally, the file descriptor
can be closed with close().

v11: Changed a couple of variables in struct eu_stall_open_properties
     from unsigned int to int.
v10: Use extension number while parsing chain of extensions.
     Remove function description for static functions.
     Move code around as per review feedback.
v9: Changed some u32 to unsigned int.
    Moved some code around as per review feedback from v8.
v8: Used div_u64 instead of / to fix 32-bit build issue.
    Changed copyright year in xe_eu_stall.c/h to 2025.
v7: Renamed input property DRM_XE_EU_STALL_PROP_EVENT_REPORT_COUNT
    to DRM_XE_EU_STALL_PROP_WAIT_NUM_REPORTS to be consistent with
    OA. Renamed the corresponding internal variables.
    Fixed some commit messages based on review feedback.
v6: Change the input sampling rate to GPU cycles instead of
    GPU cycles multiplier.

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/bb707a27975c33e4a912b9839b023acb7a1f9c90.1740533885.git.harish.chegondi@intel.com

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