bpf: Fix off-by-one error in bpf_mem_cache_idx()

bpf: Fix off-by-one error in bpf_mem_cache_idx()

[ Upstream commit 0d4567bb7e77af021301460517bc99e882521ac8 ]

According to the definition of sizes[NUM_CACHES], when the size passed
to bpf_mem_cache_size() is 256, it should return 6 instead 7.

Fixes: c6694ccf4ca3 ("bpf: Introduce any context BPF specific memory allocator.")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230118084630.3750680-1-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>