EAMxx: make rrtmgp call find_package for kokkos

If an existing install of Kokkos is used, the imported
target has local scope, so following calls to cmake's
target_link_libraries won't recognize Kokkos if the
first call to find_package was in a subdir.

In EAMxx, that's the case (it's found while parsing the
ekat subdir). However, subsequent calls to find_package
are virtually no-op, so it doesn't hurt to call it again

components/eamxx/src/physics/rrtmgp/CMakeLists.txt

@@ -127,6 +127,7 @@ yakl_process_target(rrtmgp)
 # NOTE: cannot use 'PUBLIC' in target_link_libraries,
 #       since yakl_process_target already used it
 #       with the "plain" signature
+find_package(Kokkos REQUIRED)
 target_link_libraries(rrtmgp yakl Kokkos::kokkos)
 target_include_directories(rrtmgp PUBLIC
     ${SCREAM_BASE_DIR}/../../externals/YAKL