kernel: ltq-atm: add patch fixing compilation warning for ltq_atm

Fix compilation warning caused by copy_from_user ret not handled.
Fix compilation warning:
/__w/openwrt/openwrt/openwrt/build_dir/target-mips-openwrt-linux-musl_musl/linux-lantiq_ase/ltq-atm-ase/ltq-atm/ltq_atm.c: In function 'ppe_ioctl':
/__w/openwrt/openwrt/openwrt/build_dir/target-mips-openwrt-linux-musl_musl/linux-lantiq_ase/ltq-atm-ase/ltq-atm/ltq_atm.c:341:17: error: ignoring return value of 'copy_from_user' declared with attribute 'warn_unused_result' [-Werror=unused-result]
  341 |                 copy_from_user(&mib_vcc, arg, sizeof(mib_vcc));
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Signed-off-by: Christian Marangi <[email protected]>

package/kernel/lantiq/ltq-atm/patches/100-ltq_atm-fix-compillation-warning.patch

@@ -0,0 +1,12 @@
+--- a/ltq_atm.c
++++ b/ltq_atm.c
+@@ -338,7 +338,8 @@ static int ppe_ioctl(struct atm_dev *dev
+ 		break;
+ 
+ 	case PPE_ATM_MIB_VCC:   /*  VCC related MIB */
+-		copy_from_user(&mib_vcc, arg, sizeof(mib_vcc));
++		if (copy_from_user(&mib_vcc, arg, sizeof(mib_vcc)))
++			return -EFAULT;
+ 		conn = find_vpivci(mib_vcc.vpi, mib_vcc.vci);
+ 		if (conn >= 0) {
+ 			mib_vcc.mib_vcc.aal5VccCrcErrors     = g_atm_priv_data.conn[conn].aal5_vcc_crc_err;