Thanks for the questions
I have checked the BSP and found this u-boot command seems not be enabled by default, it may be the reason of the issue you met.
We do not commonly use the u-boot to boot the M7 application, If you do want to try it, you may init SRAM by using the
mw.q 0x34100000 0x0 0x700000
Best Regards
Chenyin