Staging: gdm724x: Fix unchecked sscanf values in gdm_lte.c

This patch fixes following checkpatch.pl warning:
WARNING: unchecked sscanf value in gdm_lte.c

Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>