broadcom/vc5: Move texture return channel setup into the compiler.

The compiler decides how many LDTMUs we're going to emit, and that must
match the P1 flags.  This brings the return channel counting to a single
place (so all that's passed into the compiler is "how many return channels
you may request from this texture's format), and was a necessary step for
shadow samplers once we stop using OVRTMUOUT=0.

src/broadcom/compiler/v3d_compiler.h

@@ -215,9 +215,9 @@ enum quniform_contents {
          * A reference to a texture config parameter 1 uniform.
          *
          * This is a uniform implicitly loaded with a QPU_W_TMU* write, which
-         * defines texture width, height, filters, and wrap modes.  It will be
-         * found as a parameter to the second QOP_TEX_[STRB] instruction in a
-         * sequence.
+         * has the pointer to the indirect texture state.  Our data[] field
+         * will have a packed p1 value, but the address field will be just
+         * which texture unit's texture should be referenced.
          */
         QUNIFORM_TEXTURE_CONFIG_P1,