RTL: Disallow GPR writeback when interrupt is taken.

 On branch master
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 Changes to be committed:
	modified:   rtl/core/frv_pipeline_writeback.v

rtl/core/frv_pipeline_writeback.v

@@ -441,7 +441,7 @@ assign gpr_wide =
     fu_bit && (s4_uop == BIT_RORW) ;
 
 
-assign gpr_wen  = !s4_trap &&
+assign gpr_wen  = !s4_trap && !trap_int &&
     (csr_gpr_wen || alu_gpr_wen || lsu_gpr_wen ||
      cfu_gpr_wen || mul_gpr_wen || asi_gpr_wen ||
      bit_gpr_wen || rng_gpr_wen                );