i965: Remove unnecessary release/reference of brw_context.state.depth_region
i965: Remove unnecessary release/reference of brw_context.state.depth_region

Release the old depth region and reference the new one *only* if it has
changed.

Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Signed-off-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@intel.com>

adobe/glsl2agal,metora/MesaGLSLCompiler,dellis1972/glsl-optimizer,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,jbarczak/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,jbarczak/glsl-optimizer,jbarczak/glsl-optimizer,dellis1972/glsl-optimizer,mapbox/glsl-optimizer,mcanthony/glsl-optimizer,zeux/glsl-optimizer,adobe/glsl2agal,djreep81/glsl-optimizer,zz85/glsl-optimizer,tokyovigilante/glsl-optimizer,jbarczak/glsl-optimizer,mcanthony/glsl-optimizer,bkaradzic/glsl-optimizer,zeux/glsl-optimizer,metora/MesaGLSLCompiler,KTXSoftware/glsl2agal,benaadams/glsl-optimizer,djreep81/glsl-optimizer,tokyovigilante/glsl-optimizer,djreep81/glsl-optimizer,mapbox/glsl-optimizer,KTXSoftware/glsl2agal,bkaradzic/glsl-optimizer,wolf96/glsl-optimizer,mapbox/glsl-optimizer,zz85/glsl-optimizer,zeux/glsl-optimizer,mcanthony/glsl-optimizer,KTXSoftware/glsl2agal,benaadams/glsl-optimizer,mapbox/glsl-optimizer,KTXSoftware/glsl2agal,bkaradzic/glsl-optimizer,bkaradzic/glsl-optimizer,mapbox/glsl-optimizer,dellis1972/glsl-optimizer,KTXSoftware/glsl2agal,zz85/glsl-optimizer,wolf96/glsl-optimizer,benaadams/glsl-optimizer,adobe/glsl2agal,wolf96/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,tokyovigilante/glsl-optimizer,adobe/glsl2agal,djreep81/glsl-optimizer,adobe/glsl2agal,benaadams/glsl-optimizer,benaadams/glsl-optimizer,wolf96/glsl-optimizer,wolf96/glsl-optimizer,zz85/glsl-optimizer,zeux/glsl-optimizer,dellis1972/glsl-optimizer,zeux/glsl-optimizer,metora/MesaGLSLCompiler,tokyovigilante/glsl-optimizer,mcanthony/glsl-optimizer,mcanthony/glsl-optimizer