Fix "left shift of negative value" warning.
Fix "left shift of negative value" warning.

Fix the following warning:

ofp_rt_lookup.c: In function ‘ofp_rtl_insert’:
ofp_rt_lookup.c:151:66: warning: left shift of negative value [-Wshift-negative-value]
  uint32_t              addr = (odp_be_to_cpu_32(addr_be)) & ((~0)<<(32-masklen));

Signed-off-by: Jere Leppänen <14957520de8d9815e0c353a07fe23c737f0171e9@nokia.com>
Reviewed-by: Sorin Vultureanu <8013ba55f8675034bc2ab0d6c3a1c9650437ca36@enea.com>

OpenFastPath/ofp,TolikH/ofp,OpenFastPath/ofp,TolikH/ofp,OpenFastPath/ofp,OpenFastPath/ofp,TolikH/ofp