wifi: rtw89: fw: Remove "const" on allocation type

wifi: rtw89: fw: Remove "const" on allocation type

In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)

The assigned type is "struct rtw89_reg2_def *" but the returned type,
while technically matching, will be const qualified. As there isn't a
general way to discard "const" qualifiers, adjust the returned type to
match the assigned type. No change in allocation size results.

Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250426060935.work.049-kees@kernel.org