pan/bit: Remove BI_SHIFT stub

Fixes compile error with -Dtools=panfrost

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Fixes: 946ff9b4396 ("bifrost: Add support for nir_op_ishl")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6142>
diff --git a/src/panfrost/bifrost/test/bi_interpret.c b/src/panfrost/bifrost/test/bi_interpret.c
index a8fadb3..808b393 100644
--- a/src/panfrost/bifrost/test/bi_interpret.c
+++ b/src/panfrost/bifrost/test/bi_interpret.c
@@ -637,9 +637,6 @@
                 break;
         }
 
-        case BI_SHIFT:
-                unreachable("Unsupported op");
-
         case BI_ROUND: {
                 if (ins->roundmode == BIFROST_RTP) {
                         bfloat(bit_f64ceil, bit_f32ceil);