[bsp][wch] update v208 readme #5400

Job	Run time
RT-Thread Online Packages (STM32F407 RT-Spark)	5m 11s
RTduino/Arduino Libraries (STM32F412 Nucleo)	9m 18s
RTduino/Arduino Libraries (Raspberry Pico)	9m 8s
others_at32_hc32_ht32	5m 56s
stm32l4	7m 54s
stm32f0_f1	3m 22s
stm32_f2_f4	6m 54s
stm32_f7_g0_h7_mp15_u5_h5_wb5	3m 44s
nxp_renesas	4m 8s
nuvoton	3m 20s
gd32_n32_apm32	3m 28s
Infineon_TI_microchip	4m 51s
mips	1m 4s
aarch64	1m 4s
riscv-none	2m 10s
riscv64-unknown	1m 51s
hpmicro	1m 31s
llvm-arm	3m 22s
simulator	1m 14s
ESP32C3	6m 20s
i386-unknown	46s
nordic(yml)	7m 29s
	1h 34m 5s

Provide feedback