i965/vec4: Compare full register offsets in opt_register_coalesce nop move check.
i965/vec4: Compare full register offsets in opt_register_coalesce nop move check.

In preparation for adding support for sub-GRF offsets to the VEC4 IR.

Reviewed-by: Iago Toral Quiroga <a847aabaac44184372f6b1cd1a59aa254daaeb0b@igalia.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler