libnl: Disable debug support

libnl: Disable debug support

This dereses the size of the libnl pakcage a little bit
old:
   857 bin/packages/mips_24kc/base/libnl_3.4.0-1_mips_24kc.ipk
 41195 bin/packages/mips_24kc/base/libnl-core_3.4.0-1_mips_24kc.ipk
  7818 bin/packages/mips_24kc/base/libnl-genl_3.4.0-1_mips_24kc.ipk
 24322 bin/packages/mips_24kc/base/libnl-nf_3.4.0-1_mips_24kc.ipk
136075 bin/packages/mips_24kc/base/libnl-route_3.4.0-1_mips_24kc.ipk\ 2

new:
   852 bin/packages/mips_24kc/base/libnl_3.4.0-1_mips_24kc.ipk
 35020 bin/packages/mips_24kc/base/libnl-core_3.4.0-1_mips_24kc.ipk
  7615 bin/packages/mips_24kc/base/libnl-genl_3.4.0-1_mips_24kc.ipk
 24114 bin/packages/mips_24kc/base/libnl-nf_3.4.0-1_mips_24kc.ipk
131134 bin/packages/mips_24kc/base/libnl-route_3.4.0-1_mips_24kc.ipk

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>