Update fv3_setup with latest DT from v12

Author: mathomp4

scripts/fv3_setup

@@ -426,13 +426,13 @@ else if( $AGCM_IM <= 1120 ) then
    set USE_SHMEM = 1
    set DEF_IOS_NDS = 4
 else if( $AGCM_IM <= 1440 ) then
-   set DT = 225
+   set DT = 150
    set FV_NX = 80
    set NUM_READERS = 6
    set USE_SHMEM = 1
    set DEF_IOS_NDS = 4
 else if( $AGCM_IM <= 2880 ) then
-   set DT = 150
+   set DT = 75
    set FV_NX = 80
    set NUM_READERS = 6
    set USE_SHMEM = 1