Fixed compilation error with AOCC in TRSV

- Added a {} around zen4 switch case to avoid AOCC error.
- Error is caused because in C declarations are not a statement, therefore
  they cannot be labled hence compiler is not able to create a lable
  for jump.

AMD-Internal: [CPUPL-4880]
Change-Id: Icfeedafd80bf9a955e430ca967b6a93dcbbf075e

frame/2/trsv/bli_trsv_unf_var2_amd.c

@@ -306,6 +306,7 @@ void bli_dtrsv_unf_var2
 #if defined(BLIS_KERNELS_ZEN4)
             case BLIS_ARCH_ZEN5:
             case BLIS_ARCH_ZEN4:
+            {
 #ifdef BLIS_ENABLE_OPENMP
                 rntm_t rntm;
                 bli_rntm_init_from_global(&rntm);
@@ -324,6 +325,7 @@ void bli_dtrsv_unf_var2
                     b_fuse = 8;
                 }
                 break;
+            }
 #endif
             default:
                 kfp_af = bli_daxpyf_zen_int_16x4;