Describe the bug
The SLSTR L1B RBT product geometry files (viewing angles) are in tie point grids. When reading from satpy (which should ideally give interpolated values for an asked grid), the values seem to be getting extrapolated (values more than 360 degrees).

scn = Scene(filenames=glob(os.path.join(swath_dir, "*.nc")), reader="slstr_l1b")    
dq = DataQuery(name='satellite_azimuth_angle', stripe='a', view='nadir', resolution=500)
var_ret = load_data(dq, scn)
np.nanmax(var_ret.data)

Expected behavior
values should always in between 0 to 360 degrees for sun-earth geometry

Actual results
out: 428.0610558123558

Screenshots

Environment Info:

• OS: [ Linux]
• Satpy Version: Version: 0.53.0
• PyResample Version: Version: 1.31.0
• Readers and writers dependencies (when relevant): [run from satpy.utils import check_satpy; check_satpy()]

Additional context

• check sat_azimuth_tn in geometry_tn.nc
  if interested, file in https://drive.google.com/file/d/1CQFgiUtfOXw6KzcOL3zUnu4pU4mSCXt-/view?usp=sharing