urtwn: add an option to compile the driver without firmware specific code

[avos]

Summary

• Add URTWN_WITHOUT_UCODE option (will disable any firmware specific code when set).
• Do not exclude the driver from build when MK_SOURCELESS_UCODE is set (URTWN_WITHOUT_UCODE will be enforced unconditionally).
• Do not abort initialization when firmware cannot be loaded; behave like the URTWN_WITHOUT_UCODE option was set.
• Drop some unused variables from urtwn_softc structure.

Test Plan

Tested with RTL8188EU and RTL8188CUS in HOSTAP and STA modes.

[adrian]

wait, how's this supposed to work without firmware?

[avos]

For me, device works fine without firmware (however, firmware commands are not available in that case).

[kevlo]

Sorry I don't see the benefits of this change. If you want urtwn(4)
to be similar to the vendor driver as opposed to rewriting from scratch
like damien@ did, I suggest maybe we could implement shim layer in os_dep
directory from the Realtek's vendor source. I've had a patch set but it's
not finished yet.

[adrian]

Heh, I'm just about to pull out urtwn into sys/dev/urtwn/ before I do the RTL8188EE support. We should talk on irc about it and plan things out!

[avos]

In D4849#103153, @kevlo wrote:

Sorry I don't see the benefits of this change.

This change will allow to use the driver without external blobs + any error in the firmware download path will be treated as non-critical.

[adrian]

okay. Let's do it.