selftests: bpf: test_kmod.sh: Pass parameters to the module

It's possible to specify particular tests for test_bpf.ko with
module parameters. Make it possible to pass the module parameters,
example:

test_kmod.sh test_range=1,3

Since magnitude tests take long time it can be reasonable to skip
them.

Signed-off-by: Yauheni Kaliuta <ykaliuta@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220908120146.381218-1-ykaliuta@redhat.com