MAINTAINERS: add test_kho to KHO's entry

Commit b753522b ("kho: add test for kexec handover") introduced the
KHO test but missed adding it to KHO's MAINTAINERS entry.  Add it so the
KHO maintainers can get patches for its test.

Link: https://lkml.kernel.org/r/20251118182416.70660-1-pratyush@kernel.org


Fixes: b753522b ("kho: add test for kexec handover")
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>