Add necessary namelist entries to activate GSL GWD when using the FV3_HRRR SDF

[JeffBeck-NOAA]

DESCRIPTION OF CHANGES:

The following entries were added to the namelist YAML file to activate GSL GWD when running with the FV3_HRRR SDF:

    do_gsl_drag_ss=.true.
    do_gsl_drag_tofd=.true.
    do_gsl_drag_ls_bl=.true.

Without these flags, the GSL GWD scheme is not correctly activated.

TESTS CONDUCTED:

Tested with the RRFS_CONUS_25km domain on Hera.

ISSUE (optional):

Fixes Issue #596.

CONTRIBUTORS (optional):

@llpcarson