drm/amd/display: Implement bounds check for stream encoder creation in DCN301

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Implement bounds check for stream encoder creation in DCN301 'stream_enc_regs' array is an array of dcn10_stream_enc_registers structures. The array is initialized with four elements, corresponding to the four calls to stream_enc_regs() in the array initializer. This means that valid indices for this array are 0, 1, 2, and 3. The error message 'stream_enc_regs' 4 <= 5 below, is indicating that there is an attempt to access this array with an index of 5, which is out of bounds. This could lead to undefined behavior Here, eng_id is used as an index to access the stream_enc_regs array. If eng_id is 5, this would result in an out-of-bounds access on the stream_enc_regs array. Thus fixing Buffer overflow error in dcn301_stream_encoder_create reported by Smatch: drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn301/dcn301_resource.c:1011 dcn301_stream_encoder_create() error: buffer overflow 'stream_enc_regs' 4 <= 5