selftests/bpf: test_verifier, change names of fixup maps

Currently fixup map are named like fixup_map1, fixup_map2, and so on.
As suggested by Alexei let's change change map names such that we can
identify map type by looking at the name.

This patch is basically a find and replace change:
fixup_map1  ->  fixup_map_hash_8b
fixup_map2  ->  fixup_map_hash_48b
fixup_map3  ->  fixup_map_hash_16b
fixup_map4  ->  fixup_map_array_48b

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>