drm/xe/oa/uapi: Make OA buffer size configurable

Add a new property called DRM_XE_OA_PROPERTY_OA_BUFFER_SIZE to
allow OA buffer size to be configurable from userspace.

With this OA buffer size can be configured to any power of 2
size between 128KB and 128MB and it would default to 16MB in case
the size is not supplied.

v2:
  - Rebase
v3:
  - Add oa buffer size to capabilities [Ashutosh]
  - Address several nitpicks [Ashutosh]
  - Fix commit message/subject [Ashutosh]

BSpec: 61100, 61228
Signed-off-by: Sai Teja Pottumuttu <sai.teja.pottumuttu@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241205041913.883767-2-sai.teja.pottumuttu@intel.com

include/uapi/drm/xe_drm.h

@@ -1486,6 +1486,7 @@ struct drm_xe_oa_unit {
 	__u64 capabilities;
 #define DRM_XE_OA_CAPS_BASE		(1 << 0)
 #define DRM_XE_OA_CAPS_SYNCS		(1 << 1)
+#define DRM_XE_OA_CAPS_OA_BUFFER_SIZE	(1 << 2)
 
 	/** @oa_timestamp_freq: OA timestamp freq */
 	__u64 oa_timestamp_freq;
@@ -1651,6 +1652,14 @@ enum drm_xe_oa_property_id {
 	 * to the VM bind case.
 	 */
 	DRM_XE_OA_PROPERTY_SYNCS,
+
+	/**
+	 * @DRM_XE_OA_PROPERTY_OA_BUFFER_SIZE: Size of OA buffer to be
+	 * allocated by the driver in bytes. Supported sizes are powers of
+	 * 2 from 128 KiB to 128 MiB. When not specified, a 16 MiB OA
+	 * buffer is allocated by default.
+	 */
+	DRM_XE_OA_PROPERTY_OA_BUFFER_SIZE,
 };
 
 /**