Merge #9750: Bloomfilter: parameter variables made constant

Summary:
64aa36e param variables made const (ロハン ダル)

Tree-SHA512: 7c19f9e7dd574c8ce8a9468555f27196735b583efe349c1309c90e1e5d2949daf6891574b4bea7122d6c6aca0c7ee4a782fe3d24918d889f7bf89227084a51cd

Backport of Core PR9750
https://github.com/bitcoin/bitcoin/pull/9750/

Test Plan:

make check

Reviewers: deadalnix, Fabien, jasonbcox, markblundeberg, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: deadalnix, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3406