modules: factor out LinuxKPI based wireless drivers and add RISC-V

The LinuxKPI based wireless drivers are currently limited to amd64 and
arm64 (and until cleaned up i386). Adding RISC-V now as we have a
report that iwlwifi(4) works on RISC-V [1]. Factor the LinuxKPI based
wireless drivers out into their own block.

Given RISC-V has no ACPI support yet (though we fixed #includes in
order to keep compiling the drivers without further modifications
where possible) we need to take care of rtw89 which fails to compile
without ACPI enabled. A quick check at the Linux build files indicates
that the depenency is not correctly recorded there either. Disable
compiling rtw89 without ACPI (on RISC-V) for the moment until this is
fixed.

[1] https://mail-archive.freebsd.org/cgi/getmsg.cgi?fetch=5947+0+archive/2026/freebsd-wireless/20260112.freebsd-wireless

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D54693