intel/vec4: Set channel_sizes for MOV_INDIRECT sources

Otherwise, any indirect push constant access results in an assertion
failure when we start digging through the channel_sizes array.  This
fixes dEQP-VK.pipeline.push_constant.graphics_pipeline.dynamic_index_vert
on Haswell.  It should be a harmless no-op for GL since indirect push
constants aren't used there.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Fixes: e69e5c7006 "i965/vec4: load dvec3/4 uniforms first in the..."

src/intel/compiler/brw_vec4.cpp

@@ -695,8 +695,11 @@ vec4_visitor::pack_uniform_registers()
           * the next part of our packing algorithm.
           */
          int reg = inst->src[0].nr;
-         for (unsigned i = 0; i < vec4s_read; i++)
+         int channel_size = type_sz(inst->src[0].type) / 4;
+         for (unsigned i = 0; i < vec4s_read; i++) {
             chans_used[reg + i] = 4;
+            channel_sizes[reg + i] = MAX2(channel_sizes[reg + i], channel_size);
+         }
       }
    }