[drivers][serial/v2] fix missing break after -RT_EPERM when buf size is 0 #3802

Job	Run time
A9-rtsmart :default.cfg	1m 21s
RISCV :default.cfg	1m 31s
RISCV-smp :default.cfg	1m 35s
A9 :kernel/kernel_basic.cfg	6m 40s
A9-rtsmart :kernel/kernel_basic.cfg	6m 29s
A9 :kernel/ipc.cfg	5m 16s
A9 :kernel/mem.cfg	1m 22s
XUANTIE-rtsmart :default.cfg	1m 49s
XUANTIE-rtsmart :kernel/ipc.cfg	6m 20s
RISCV-rtsmart :default.cfg	1m 11s
A9 :default.cfg	1m 23s
XUANTIE-rtsmart :kernel/mem.cfg	2m 0s
RISCV :kernel/mem.cfg	1m 15s
RISCV :kernel/atomic_c11.cfg	1m 18s
A9-rtsmart :kernel/mem.cfg	1m 21s
A9-smp :default.cfg	1m 41s
AARCH64-smp :kernel/mem.cfg	1m 38s
XUANTIE-rtsmart :kernel/kernel_basic.cfg	7m 20s
A9 :components/lwip.cfg	1m 40s
AARCH64-rtsmart :default.cfg	1m 21s
AARCH64 :default.cfg	1m 14s
A9-smp :kernel/ipc.cfg	5m 28s
A9-rtsmart :kernel/ipc.cfg	5m 35s
AARCH64-rtsmart :kernel/mem.cfg	1m 15s
AARCH64-smp :default.cfg	1m 26s
A9 :components/sal.cfg	1m 37s
A9-smp :kernel/mem.cfg	1m 36s
RISCV-rtsmart :kernel/ipc.cfg	5m 29s
RISCV :kernel/ipc.cfg	5m 16s
RISCV-rtsmart :kernel/kernel_basic.cfg	6m 35s
AARCH64 :kernel/mem.cfg	1m 9s
RISCV-smp :kernel/mem.cfg	1m 44s
A9 :kernel/atomic_c11.cfg	1m 9s
A9 :cpp11/cpp11.cfg	1m 17s
RISCV-rtsmart :kernel/mem.cfg	1m 11s
A9-smp :kernel/kernel_basic.cfg	6m 50s
RISCV :kernel/kernel_basic.cfg	6m 49s
A9 :components/netdev.cfg	1m 43s
A9 :components/dfs.cfg	1m 27s
	1h 53m 21s

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