`VK_EXT_acquire_drm_display` is misusing `VK_ERROR_UNKNOWN`

`vkAcquireDrmDisplayEXT` and `vkGetDrmDisplayEXT` defines when they return `VK_ERROR_UNKNOWN`. That goes against what the error code is for:

> `VK_ERROR_UNKNOWN` is not expected to ever be returned if the application behavior is valid

They sould instead return something like `VK_ERROR_INITIALIZATION_FAILED` or specific new error code indicative of the specific problem.

PS: Additionally, `vkGetImageViewAddressNVX` and `vkLatencySleepNV` list `VK_ERROR_UNKNOWN` as a possible return code. Initially I thought I would just PR to remove it, but this may be indicative the drivers possibly try to actively return it for something, so the vendors should probably be queried about that.