certs/blacklist_hashes.c: fix const confusion in certs blacklist

This file fails to compile as follows:

  CC      certs/blacklist_hashes.o
certs/blacklist_hashes.c:4:1: error: ignoring attribute ‘section (".init.data")’ because it conflicts with previous ‘section (".init.rodata")’ [-Werror=attributes]
    4 | const char __initdata *const blacklist_hashes[] = {
      | ^~~~~
In file included from certs/blacklist_hashes.c:2:
certs/blacklist.h:5:38: note: previous declaration here
    5 | extern const char __initconst *const blacklist_hashes[];
      |                                      ^~~~~~~~~~~~~~~~

Apply the same fix as commit 2be04df5 ("certs/blacklist_nohashes.c:
fix const confusion in certs blacklist").

Fixes: 734114f8

 ("KEYS: Add a system blacklist keyring")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Mickaël Salaün <mic@linux.microsoft.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>