D3D12: Fixed cubemap blit.
D3D12: Fixed cubemap blit.

mendsley/bgfx,kondrak/bgfx,LSBOSS/bgfx,LSBOSS/bgfx,MikePopoloski/bgfx,LWJGL-CI/bgfx,aonorin/bgfx,fluffyfreak/bgfx,elmindreda/bgfx,attilaz/bgfx,emoon/bgfx,cuavas/bgfx,mmicko/bgfx,andr3wmac/bgfx,andr3wmac/bgfx,marco-we/bgfx,darkimage/bgfx,bkaradzic/bgfx,attilaz/bgfx,elmindreda/bgfx,MikePopoloski/bgfx,mendsley/bgfx,cuavas/bgfx,marco-we/bgfx,v3n/bgfx,attilaz/bgfx,mendsley/bgfx,jpcy/bgfx,marco-we/bgfx,v3n/bgfx,LSBOSS/bgfx,jdryg/bgfx,LWJGL-CI/bgfx,jdryg/bgfx,fluffyfreak/bgfx,jpcy/bgfx,cuavas/bgfx,kondrak/bgfx,LWJGL-CI/bgfx,aonorin/bgfx,v3n/bgfx,jdryg/bgfx,LWJGL-CI/bgfx,andr3wmac/bgfx,fluffyfreak/bgfx,MikePopoloski/bgfx,jpcy/bgfx,emoon/bgfx,darkimage/bgfx,fluffyfreak/bgfx,bkaradzic/bgfx,bkaradzic/bgfx,darkimage/bgfx,jdryg/bgfx,Synxis/bgfx,mmicko/bgfx,aonorin/bgfx,0-wiz-0/bgfx,elmindreda/bgfx,mmicko/bgfx,emoon/bgfx,0-wiz-0/bgfx,kondrak/bgfx,Synxis/bgfx,bkaradzic/bgfx,septag/bgfx,septag/bgfx,septag/bgfx,jpcy/bgfx,0-wiz-0/bgfx,Synxis/bgfx