btf: remove redundant CONFIG_BPF test in scripts/link-vmlinux.sh

btf: remove redundant CONFIG_BPF test in scripts/link-vmlinux.sh

CONFIG_DEBUG_INFO_BTF depends on CONFIG_BPF_SYSCALL, which in turn
selects CONFIG_BPF.

When CONFIG_DEBUG_INFO_BTF=y, CONFIG_BPF=y is always met.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240913173759.1316390-1-masahiroy@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>