bpf: add support for map_name and map_ifindex fields in BPF_MAP_CREATE

bpf: add support for map_name and map_ifindex fields in BPF_MAP_CREATE

* bpf.c (BEGIN_BPF_CMD_DECODER(BPF_MAP_CREATE)): Decode map_name
and map_ifindex fields that were added in Linux commits
v4.15-rc1~84^2~605^2~3 and v4.16-rc1~123^2~145^2~5^2~8, respectively.
* bpf_attr.h (struct BPF_MAP_CREATE_struct): Add map_name
and map_ifindex fields.
* tests/bpf.c (init_BPF_MAP_CREATE_attr7): New function.
(BPF_MAP_CREATE_checks): Remove const qualifier, add two more checks.