drm/i915/uapi/pxp: Add a GET_PARAM for PXP

Because of the additional firmware, component-driver and
initialization depedencies required on MTL platform before a
PXP context can be created, UMD calling for PXP creation as a
way to get-caps can take a long time. An actual real world
customer stack has seen this happen in the 4-to-8 second range
after the kernel starts (which sees MESA's init appear in the
middle of this range as the compositor comes up). To avoid
unncessary delays experienced by the UMD for get-caps purposes,
add a GET_PARAM for I915_PARAM_PXP_SUPPORT.

However, some failures can still occur after all the depedencies
are met (such as firmware init flow failure, bios configurations
or SOC fusing not allowing PXP enablement). Those scenarios will
only be known to user space when it attempts creating a PXP context
and is documented in the GEM UAPI headers.

While making this change, create a helper that is common to both
GET_PARAM caller and intel_pxp_start since the latter does
similar checks.

Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230511231738.1077674-7-alan.previn.teres.alexis@intel.com