linux-intel/5.4: drop recipe

New LTS 5.15 is already added, so time to drop 5.4 support

Drop linux-intel-rt/5.4 too.

Drop cfg which is not required for LTS 5.10 & 5.15.

Ref:
https://github.com/torvalds/linux/commit/eb83479e18999e34b3b800f54aa31137f7f41c33



Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>