[REVERT] drm/radeon: consolidate vga and dvi get_modes functions (v2)

[Tony Vroon]

Please consider reverting commit 3e22920fbd0005927bc41f71daeb056a0f4def82 by title of:
drm/radeon: consolidate vga and dvi get_modes functions (v2)

I have bisected this as the culprit for my PowerMac 7,3 crashing back into OpenFirmware 
very early at boot with an invalid memory access. The diagnostic data printed is:
%SSR0: 0000000.00c00000
%SSR1: 1000000.0083030

Regards,
Tony V.