target/riscv: Silence -Werror=return-type

- clang compains about the functions not returning a value

src/target/riscv/asm.h

@@ -17,6 +17,7 @@ static uint32_t load(const struct target *target, unsigned int rd,
 			return ld(rd, base, offset);
 	}
 	assert(0);
+    return 0; // Silence -Werror=return-type
 }
 
 static uint32_t store(const struct target *target, unsigned int src,
@@ -31,6 +32,7 @@ static uint32_t store(const struct target *target, unsigned int src,
 			return sd(src, base, offset);
 	}
 	assert(0);
+    return 0; // Silence -Werror=return-type
 }
 
 #endif

src/target/riscv/riscv-011.c

@@ -269,6 +269,7 @@ static unsigned int slot_offset(const struct target *target, slot_t slot)
 	LOG_ERROR("slot_offset called with xlen=%d, slot=%d",
 			riscv_xlen(target), slot);
 	assert(0);
+	return 0; // Silence -Werror=return-type
 }
 
 static uint32_t load_slot(const struct target *target, unsigned int dest,