intel/compiler: Fix a fallthrough in components_read() for atomics

In commit 284f0c9a57 I refactored the
handling of the data source to just call a helper rather than special
casing opcodes with 0 or 2 sources.  Unfortunately, I also dropped the
"else return 1", creating a fallthrough for all sources other than
SURFACE_LOGICAL_SRC_ADDRESS and SURFACE_LOGICAL_SRC_DATA.

The case below happened to return the correct value for all cases except
SURFACE_LOGICAL_SRC_SURFACE, which has been returning 2 instead of 1
since that commit.

Restore the else case.  Thanks to Marcin Ślusarz for catching this.

Fixes: 284f0c9a57 ("intel/compiler: Add an lsc_op_num_data_values() helper")
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23347>

src/intel/compiler/brw_fs.cpp

@@ -825,6 +825,8 @@ fs_inst::components_read(unsigned i) const
       /* Surface operation source. */
       else if (i == SURFACE_LOGICAL_SRC_DATA)
          return lsc_op_num_data_values(op);
+      else
+         return 1;
    }
    case FS_OPCODE_INTERPOLATE_AT_PER_SLOT_OFFSET:
       return (i == 0 ? 2 : 1);