drm/i915/jsl: s/JSL/JASPERLAKE for platform/subplatform defines

Follow consistent naming convention. Replace JSL with
JASPERLAKE. Unroll IS_JSL_EHL() define  with IS_JASPERLAKE() ||
IS_ELKHARTLAKE() condition. Change in the display step define for
Jasperlake.

v2:
- Change subject prefix skl instead of SKL(Anusha)

v3:
- Remove the use of define IS_JSL_EHL.
- Replace with IS_JASPERLAKE() || IS_ELKHARTLAKE()
- Unrolled wrapper IS_JSL_ELK_DISPLAY_STEP (Jani/Tvrtko)

v4:
- Removed unused macro

v5:
- Resolved valid checkpatch warning(Jani)

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230801135344.3797924-9-dnyaneshwar.bhadane@intel.com