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