agx: Remove bogus assert

I->mask isn't even valid for iter instructions.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22891>

src/asahi/compiler/agx_pack.c

@@ -525,7 +525,6 @@ agx_pack_instr(struct util_dynarray *emission, struct util_dynarray *fixups,
       bool flat = (I->op == AGX_OPCODE_LDCF);
       unsigned D = agx_pack_alu_dst(I->dest[0]);
       unsigned channels = (I->channels & 0x3);
-      assert(I->mask < 0xF); /* 0 indicates full mask */
 
       agx_index src_I = I->src[0];
       assert(src_I.type == AGX_INDEX_IMMEDIATE);