Add Arch Linux 7 rcraid support

[jameswright1562]

Summary

• Include the patched AMD rcraid source and rcblob.x86_64 needed to build the driver.
• Include the verified rcraid.ko built against Arch Linux 7.1.4 headers.
• Keep transient build files and the downloaded AMD driver archive ignored.

Why

The working driver support was previously hidden by dkms/rcraid/src/* in .gitignore. This change makes the Linux 7 header compatibility work and the validated Arch build inputs visible for review and reuse.

Validation

• Confirmed the module was built against Arch Linux 7.1.4 headers.
• Confirmed source compatibility changes in Makefile, rc_init.c, and rc_msg.c.
• Confirmed the binary blob patch at offsets 0x1190 and 0x5ccfe.
• Confirmed generated objects and the downloaded vendor archive remain ignored.

Licensing note

The included AMD source, binary blob, and module remain subject to AMD's applicable license terms.

Following steps

• Reverse .gitignore dkms/src changes in a separate PR