drm/amdgpu: simplify return statement in amdgpu_ras_eeprom_init
Remove the logically dead code in the last return statement of
amdgpu_ras_eeprom_init. The condition res < 0 is redundant since
res is already checked for a negative value earlier. Replace
return res < 0 ? res : 0; with return 0 to improve clarity.